As more of our vacation memories end up online (thanks to the ubiquity and affordability of digital cameras), fierce competition is brewing among websites and smart phone apps to become your go-to tool for showing off and storing photos.

But there is a lot to consider before you upload. The website you choose should be “high-voltage”—meaning it should have millions of members and be thriving financially—to spare you from the danger of needing to move your photos to a new provider every few years. The site or app should make it easy to share images with anyone in the world, not just members. It's also critical that you have the option of unlimited storage and the ability to upload images in large file sizes. Easy-to-control privacy settings are a must, allowing users to share selected photos with specified contacts only.

For travellers in particular, photo-sharing sites should make smart use of camera-generated geo-location data, automatically plotting your photos on a map. A good photo-sharing site should also allow for speedy uploads from mobile devices and provide some basic photo-editing options for quick touch-ups on the fly.

Using that basic criteria, here are my picks for the best photo-sharing and image-storing sites, with the typical camera-toting wanderer in mind.

The most popular site – and the gold standard -- for sharing and storing photos. 

With six billion photos, this Yahoo-owned site isn't disappearing any time soon. For photo-sharing beginners, a no-frills Flickr account is a good starting place because it has the fastest, most intuitive process for uploading photos from your computer or mobile device. Apple's latest version of its iPhoto software, for instance, includes a one-click service for uploading photos to a Flickr account, and Flickr apps allow you to upload images quickly from smart phones, too. Free accounts allow for the upload of 300 megabytes' worth of imagery each month, or about 100 standard-sized photos, and photo geo-tagging is automatic. (If you want to keep your favourite mountaintop retreat a secret, simply turn off the geo-location feature on your camera or on Flickr.) Once an image is posted, you can e-mail a copy of the image (with a link, for downloading it) to anyone, even if they don't belong to Flickr.

Pro accounts cost $25 a year and offer unlimited uploads, but owners of DSLR cameras (which often shoot in large file sizes), may be frustrated with its caps on image sizes, such as its 15 megabyte limit for free accounts. Basic photo editing tools, via partner service Picnik, are free.

In an innovative photo-sharing development, this autumn Flickr debuted Photo Sessions, which allows a group of people (including non-members, via invitation) to flip through the same online photo album in real-time on different browsers -- think of it as the 1970s rec room slideshow updated to the era of iPads.

The 800-pound gorilla of social-networking fame stores more photos than any other website and makes sharing easy, but it doesn't present photographs well.

The giant social-networking site has 800 million users, which probably includes most of the family and friends you might want to share your holiday snaps with. Sharing is incredibly easy, though the complexity of understanding the site's privacy settings is well known. In a plus, Facebook is well integrated with computer software and cameras; iPhoto, for instance, allows you to upload photos with one click.

Facebook doesn't offer any built-in photo-editing tools, but the company says it will soon roll out a handful of "filters", such as the option to turn colour images into black-and-white, or 1970s-print-style, shots. Another big flaw: You can't export your photos back out of Facebook, should you ever wish to, unless you download each image one by one. Other flaws include stiff limits on the size of images that can be uploaded, meaning essentially that photos shot on a DSLR will be re-sized and not look as impressive, and Facebook doesn't automatically collect and map out any geo-location data recorded by cameras (excluding some from smart phones). In brief, opt for Facebook if you already enjoy using the site and if your main goal is to share simple images with friends and family, most of whom also belong to the site, rather than impressing strangers with your photographic prowess.

The social networking site newcomer has had its greatest success with travel photographers keen to garner a following.

The fate of Google+ is still up in the air, but if there is one group of people who have wholeheartedly embraced the site, it is photographers. The free social networking site's default presentation of photos is in large format (2048 pixels on their longest edge), which is more than the tiny default image size of Facebook. Travel photographers can also amass larger followers for their artworks. Case in point: Trey Ratcliff has attracted more than 300,000 followers of his travel photography since the site launched this summer. The site's privacy settings are as effective as Facebook's and Flickr's.

Google+ works in tandem with the search giant's longstanding Picasa and Picasa Web Albums photo tools, which offer the storing of up to a gigabyte of photos for free, the uploading of large photos and the exporting of photos to another service (should you decide one day to leave). Picasa also makes it easy to complete basic image edits and to upload images via a mobile device. If your camera records geo-location data and you've chosen the correct settings, photos will be automatically plotted on a map on Google's tools. In short, pick Google+ if you're trying to build an audience of admirers for your photographic work and if you don't mind having to constantly e-mail the web album links to friends and family who aren't Google+ members yet.

Best for travellers whose priority is making high quality photo books and prints.

This thriving site isn't as hip or hyped as some of the others, but it excels at creating affordable, high-quality prints and photos books. No other photo-sharing site comes close on this score, even those that provide photo-printing functions. Accounts are free and allow unlimited storage of a modest number of photos. You can share images by e-mailing a link to members and non-members of the site. However, geo-location data plotting, mobile-device uploading, and some other travel-related features are limited in scope. To summarise, Snapfish is best for people using their desktops at home to select a few photos to print.

The top site for creating eye-popping, online photographic portfolios.

The most buzzed-about photo-sharing site of the year actually began in 2003 in Toronto, aimed at camera-savvy folk who know their apertures from their F-stops. A re-design in 2009 that focused on presenting photos in the largest, prettiest format possible —a la the Boston Globe's Big Picture feature—has made the site a sensation among the fine art, travel and wedding photographer crowds.

Free accounts provide a taster of how the service works, but it is only the paid accounts that deliver substantial functionality. Paid accounts cost $50 a year, and come with unlimited uploads, the largest file size limits of any major photo-sharing site and an embed code for most postings, allowing you to easily publish the image on your own website or blog. 500px also has the broadest international membership of any of the other sites mentioned, which means that photographs receive comments from a global community, which can be a plus to travel photographers.

On the downside, the site has grown about 500% in the past year and has had trouble moderating content. If you explore other members’ pages you may stumble upon some not-safe-for-work material. It's also not entirely clear how to export photos back off the site if you decide you're unhappy with the service.

If the only camera you use is your smartphone, this free app is the easiest way to share your photos.

Instagram is only a year old, but the app has already has been downloaded by 11 million users, most of whom are young. The app is often used to throw filters onto pictures, such as transforming a shot digitally to make it look like it was taken on a 1970s Polaroid-style print camera. But you don't need to use those filters to take advantage of the app's ability to easily share your photos via Facebook, Twitter, e-mail, text -- or wherever your friends and family are online. When one-touch simplicity and inexpensiveness is paramount, Instagram is your best, free option if you take most of your photos on an iPhone.

The biggest rival to Flickr, this tried-and-tested site hasn't done anything innovative in a long time, but it has the photo-sharing basics down pat.

With 23 million users every month and eight billion images uploaded since 2003, Photobucket is a close rival to Flickr. It has recently become the main photo-sharing tool that Twitter uses to power photo uploading for its users. The site is free and provides unlimited storage, but it imposes caps on the size of images. Integration with Facebook and Twitter is seamless, and iPhone and Android apps make it easy to upload photos via your smart phone. Its biggest failing is that it tends to be slower than other sites, taking longer to load images and requiring more steps to see pictures in full size.

Sean O'Neill is the tech travel columnist for BBC Travel