noobracer, I have many of each and you'll probably be happy with either one, but to answer your questions:
1) X; but both have good enough range to go almost as far as you can see them.
2) Lots! The 4WD gives a big advantage. The Z is really easy to spin until you start upgrading it.
3) Z by a landslide. The X doens't have many hop-ups as it's near perfect out of the box. The Z needs some hopping up to bring it up to snuff.
4) I have not had this problem at all.
5) Mini-X.
Do you have any other RCs? If you're coming from 1/10, consider the X, if you only have Bits etc., then go for the Z, the X is a little tricky for a first RC. Check out
http://mini-zracer.com for more Z info. Thanks!