At this point it is hard for me to get excited about either in any ecstatic way because what it comes down to is all about the content and really there isn't much to show at a press release like E3. There is so much that is subject to change also not just on the hardware side but also on the software side as well and that it makes hard to say "I WANT THAT ONE SANTA!" If you look at the PS3 is theoretically superior to the 360 as far as performance but you have to know what you are doing with it, the same is going to be true with these devices. If they can't get the hardware to succeed then it's just gonna fall flat on many titles but have that one that is a diamond in the rough, like God of War 3.
There is another other point and that is they have two different audiences Nintendo has been about Kids and casual where Sony has been about young adults to mature. It will be interesting to see if Sony stays on that hard nose mature line or push for more casual gaming to try and compete with Nintendo's DS a little more head on.
I just right now think it's a little early to start looking at who could be the best performer when the meat, bones and etc (the games) that will carry those units haven't really come out of the gate yet, most notably 3rd party. Especially when we don't know for sure what direction Sony is going.