I'm not sure why you would ask this question, because the 3ds will always be choosed 'cause it has many more functions and it's currently the self-proclaimed best handeheld available.
But this is a very simple question, not worth being a thread. Could even consider it spam but, eh.
Don't argue with idiots because they will drag you down to their level and then beat you with experience.
I VOTE FOR DSi :I My mom is always saying the 3DS screen is too small,so she won't even buy it for me :l HEY MOM,YOU PAID FOR THE DS,SAME SCREEN SIZE :U
So i took a bus to walmart after i heard the rumor that a Godly nintendo stand contained a Playable 3DS in it.
I saw it, it was so beatifull that i began to touch it slowly, opened it.....then tried the oh-so-awesome circle pad, smooth and comfortable, then i noticed a little thing below the 3DS, it said the features of the 3DS and "Presenting: Street fighter FFIV!.
So i turned it on, took the 3D bar to the top, and experienced the best feeling of handheld gaming in my whole life.
I would (obviously) pick a 3DS
I prefer the DSi, cause it is much more bigger, and has bigger screens too, but the 3DS has a superior resolution and well, 3D.
Once upon a time in a big canadian city know as "Timmins" a young man went to a well know electronic store called "Future Shop".
The young man started browsing the store, then he stopped. looked to the left and saw a 3DS test section.
The young man wiped the drool of his chin and procced to the 3DS. His hands wrapped around the 3DS perfectly.
As he turned it on he was amsed the man said: "WOW" as he played splinter cell 3D he was hooked and he knew that was the perfect system for a hardcore gamer like him.
But, this all happend before the price drop, and the man only had $67, so he had to give up the amasement and left.
I choose the 3DS, because for one thing u can have the internet and the dsi had internet but it didnt take u to the website & the 3DS does. I also like the 3D on it and the friend list is fantastic I also like that we get notifications about games, and more. I like that we can draw in it.