Hi Rachel,
I don't think you should get a carpet python, they suck :P
JUST KIDDING!

Both are great snakes, but I prefer IJs. They are smaller (4-6ft versus 5-7+ft), easier to tame (jungles tend to be nippier) and I just love their colour pattern.
However, jungles are beautiful as well, it's really a matter of taste.
I'd take a look at some pics online and decide which you like better. Also, what size are you looking for? IJs are smaller, and range from 99% terrestial to 99% arboreal. Jungles are bigger, and I believe more arboreal. But it varies.
And does a little nippiness bother you? They are all nippy as babies, but my IJ's have never bitten me (well, once through a feeding mistake) or even struck, but the jungles I've met have been more put-offish :]
Either way, Rachel, you can't go wrong with a carpet!!
Keep us updated!
Zoe