Hmm well I'm not familiar with the cloud storage feature so I can't tell you much about the differences, but I might be able to help you with transferring to a PC or PS3.

Firstly, you have the option of wirelessly transferring, or wired transferring.  I'd recommend hooking it up if you're transferring games or big files, because it will take A LOT longer wirelessly.

You download the content manager program for your computer online.  There's a website for it, it shouldn't take you very long to find it by searching for it on google or something.

You will then run the program on your computer, and then your Vita.  You can also set the program to run in the system tray, and I think it works automatically when you hook up your Vita.

Then you have to select whether you are transferring data from the PC to the Vita, or the Vita to the PC.  Everything is handled on your Vita's screen.

There are a few different categories, I can't remember all of them now.  There's one for Vita DLC, one for PSOne Classic game saves, one for all of your Vita's games and programs...  You'll have to do some exploring there because I can't remember exactly how it's all set up right now.

If you want to transfer videos, music and pictures, then it opens up the video, music or picture program alongside the content manager program, and you handle the transfer in those programs.  It can be a little annoying, but it works out fine.

I hope this helps answer some of your questions.  If there's something more specific you'd like to know about then let us know.  I could maybe check it out later tonight after work.