I'm looking at two Cinelli road stems the AX and the EX. It looks like the difference is the bottom end that goes into the headset(sorry, not sure of the tech term). One has the wedge the other is bored out and cut up the side. Any benifits or disadvantages to either one?

The 'quill' is the portion that fits into the fork steerer. I have found that both styles are equally effective.

i agree. they both work fine.

'XA' and/or 'XE' actually. (big fan of Cinelli quills, especially the XA )

"especially the XA "

Why?

The Cinelli logo on the XE is a sticker, whereas on the XA it's a drilled & recessed plastic button (looks much nicer IMO)

The XA's clamp is serrated on the inside for a better grip, the XE is smooth.

The expander-bolt retention mechanism on the XA seems more elegant to me than the XE's wedge-jam.

I've got a few of both, and the XA's are becomming VERY hard to find. The XE's may actually still be in current production, not sure.

Do you notice that you can adjust the height of one more than the other?

No real difference on insertion and adjustment.