As a programming student, I'd like any platform I can get to work on. I already have the Petit DSiWare title on my 3DS, though. What, if anything, makes Smile better?

It is exactly petit, but with so much more, and makes the games being made have less limitations

User Defined Functions makes this version leagues better than it's predecessor.

1-99999 lines of code

The improvements are too legion to fit in a Miiverse post. Check out smilebasic.com and take a look through the technical specs and the instruction list. It feels less like a toy and more like a handheld development studio.