Kind of depends what you want to do. If you own a Lumia, then Nokia Camera is the best you can get with no cost. It has all the pro functions you could want.
As for the differences, you'd have to give them a swing yourself and determine if it suits you or not. I'd say that out of the ones listed, Nokia Camera and ProShot (with ProShot having more functions) are similar.
Most other apps tend to have specific functions, similar to the built-in camera app (night, portarait, etc) with some add-ons and then some have filters. Most have a trial you can check out.