Right now, all my my betting money's on the PlayStation 3. Not only does the system have more experience entertaining gamers, it also has many more games that attract me as a customer. In the Vita's corner this contender is asking for a higher price than some people are willing to spend. Having only released less than a year ago, the Vita doesn't have very many games that scream "BUY ME!" The ability to customize your playstyle also seems a little too profound. Like the PSP before it, the VIta can sync up with the PlayStation 3, but seems to have more potency in that area. Given that I wasn't the biggest fan of the PSP either, I have my doubts that the Vita will obtain strong affections in the longrun.
They are both great. Personally, I don't compare consoles to handhelds. Unless the console maker messes up, it will be better. The PS3 can do a lot more than the Vita. It just can't do it on the go. My Vita has seen a lot more use since LBP Vita (the first "wave" of games since launch) but I still spend more time on the PS3.