You forgot to put the vita on your poll. But, I went with the ps3. I'm a fan of the entire ps ecosystem, and own both a psp and vita, which I'm also fond of, and also happen to have a ps4. I want the ps4 to be my platform of choice, but that probably won't happen till next year when it gets more games. Funny enough though, my most anticipated title is not on the ps4 or even the ps3, but on the vita. I'm really looking forward to Danganronpa in February.
Anyways, I just like the selection of games across Sony platforms, and all those systems are as familiar to me as the back of my hand. Plus, they're region free. The consoles are easy to work with, and I love playing content from the UK and Japan on my NA ps3. The psp is a bit of a hassle, but there's a trick to it that involves the ps3. The vita's not worth messing around with, since changing the account activation involves reformatting the entire system, but I still enjoy it for NA content.
Plus, as a company, I respect Sony more than the other two companies combined. Granted, I absolutely hate MS, and refuse to send any money their way if possible, hence why I've never owned an xbox, and don't have a gaming pc, despite being tempted to get one for indie titles. Ninty and I go way back, but I do have some issues with the way they do things. Sure, Ninty's good points keep me coming back to them, but I respect Sony more.