I just got a Tamagotchi P's and I love the way it feels in my hand. It's very light and smooth. I just started it up, but I love the way you can personalize your profile and the concept of the Deco Pierces is very enticing. It's definitely more complex than the Tamagotchi iD L but this adds to the experience as long as you aren't too busy.
My iD L is wonderful too, and the way everything is structured really helped me understand the Tamagotchi P's much more easily. It has a much more simple gameplay, which is good for me during the school year because I am usually pressed for time when I have school.
Both my iD L and P's are in Japanese (though the iD L is available in English now for a pretty high price). I haven't found this to be too much of a problem; it got me very interested in learning Hiragana and Katakana so I can sound out almost everything that is on the screen in Japanese characters.
Personally, I would get the one I saw for the lowest price. If you get an iD L, you could get a Tamagotchi P's later, and you'll be able to find more information about the Tamagotchi P's if you wait a little while. The Tamagotchi P's is full of surprises!