Yeah, I can vouch for the fact that handhelds are now getting the lion's share of the best (IMO) RPG's.
The PSP (if you just want one to play games on), I would think, could be bought very cheaply now -and- its RPG's look & sound MUCH better than they do on the DS...also - if (like me:) you're more of a "Big-Screen" kinda' guy/gal, w/ the PSP, you have the option & ability to output your video games to display on a big screen/HDTV.
The DS *also* has a lot of good RPG's on it, though
AND -the 3DS looks to be stealing almost all of the present/upcoming RPG's
If I were you, I would:
A). Get a cheap & basic (used or new) PSP (+ the video output cables, if you like), and
B). Get a 3DS-XL.
Between the PSP, the 3DS' b/c with older DS games + all of the RPG's it already has (and looks like there's more coming)...you'd have your bases pretty well covered
Of course, if you don't like/play RPG's - my opinions & experiences won't be of much help to you