As for the looks I prefer a Jungle.....if it's a really nice example. I would prefer a nice IJ over a poor Jungle.
I don't keep either so I can't comment on any activity difference, if any. My Coastal is pretty active at night.
My IJ's are both pretty active, even during the day. They rarely spend time in their hides, they prefer to drape over a log or hang out on a shelf/perch. Carpets are great display snakes!
It's up to you on the looks, I really like IJ's though
We have a bunch, and I see no difference in behavior. Both are smaller carpets and will make use of any perches/branches you place in the cage. Great display snakes.