What are the differences between the two? I know the engines are different, but what else? Are they about the same size?
I have both a Kitty Kat and a POLARIS 120 (I know you asked about an ARCTIC 120, but they're similar).
The Kitty Kat is an P.O.S, IMHO. It doesn't even want to go through, let's say 6 inches snow, barely goes up an incline, where with the 120, it's not a problem at all.
The 120's have a wider ski stance, more reliable 4-stroke engine, way more suspension travel.
I've seen used 120's for $ 700 in GOOD condition.
The POLARIS 120's from 2000 to 2013 are pretty much identical, so if you can find a deal on a used older 120, as long as it's in good condition, don't hesitate to but it just cause it's a 2000 or 2001 model.
Sorry, I don't know what year ARCTIC CAT's 120's are similar to the current ones.
Santa brought a pink 120 to my daughter when she was 3 1/2, and it was probably her favorite gift of all.
Hope this helps