I just wanted to give my 2 cents on this one as well.
There has been a lot of fandom discussion between these two so it all comes down to - what do you want to get out of a caching plugin solution.
You can always break it down to pros and cons of each plugin but at this point those are all general and may or may not concern you:
- both are easy to implement the CDN with ( though both fail to do the url rewrite if your server is running with PHP 7+
- both are widely used so any issues can be addressed reasonably fast.
- W3TC has a great page cache feature that can address latency issues pretty well, but it's minify solution is known for breaking a lot of themes out there so be careful with it.
- W3TC comes with premium version ( which offers fragment caching) but general opinion is that it doesn't really change much when it comes to the end user experience (and in the bottom line that is what most people are striving for).
- W3TC rarely updates which can be something that you might find interesting.
- W3TC does provide with a much more robust solution which allows for a more custom experience if you're looking for one - but it also works pretty well out of the box.
- WPSC provides solid results and is more resource friendly then W3TC
- It's url rewrite engine is based on CDN Linker which is regex based so if you're looking to run a CDN with it. However, both WPSC and W3TC fail to rewrite urls with PHP 7+ which is something that is looking to be patched soon (but knowing the release schedule for W3TC is not as likely)
- Both allow you to drop the cache fairly easy which is a good thing - any changes that you make and are looking to have applied right away will be addressed.
- WPSC does not provide with API linking solution ( W3TC does) which you can use to link your CDN account with your plugin and purge the CDN cache from the plugin - which can be a useful feature if you're looking to have everyting in one place and not have to login into multiple different panels in order for your changes to apply.
So, with this being said - it's all up to what you're looking to get. If it's speed and optimization the answer is simple: install one of these, configure it to your preference and run a speed test ( pingdom is a good reference tool) and take a note of the speed increase, and the various grades that you are looking to improve. Run a top on your server and check the resource utilization and see if the server is in good shape. Disable the plugin, install the other one - and repeat the process.
What works for me might not work for you and vice-versa. It would be awesome if you could share the test results with us - it would give us an insight in this endless dilemma.