i had to make a similar decision a week ago when I was thinking about getting my first 3ds/2ds. initially i wanted to get a 2ds too because i did not care about the 3d effect and it was cheaper. then I found out that there will be a new version in mid February. after some investigation I decided to wait for the new 3ds XL.
the main reasons for my decision were:
- better hardware. cpu and gpu speed doubled. ram and vram doubled too. so there might be new games coming out in the future that you can not play on the old 2ds/3ds
- new buttons. c-stick + 2 extra shoulder buttons
so I basically decided to go with the future proof hardware. right now it probably does not matter whether you get a 2ds or a n3ds but future games might play more comfortably on the new console. or they can not be played on the old consoles at all.
btw: there is a nice comparision between all 5 consoles (2ds, 3ds, 3dsxl, n3ds, n3dsxl):