I have a chopped Naomi and a NAC.
E2's are always in demand and tend to fetch higher prices. NACs are generally more plentiful and you should be able to pick one up easier as you have seen from ebay.
They both have a MS9 15/24k monitor. The E2 has a rotate mech which makes rotating the monitor slightly easier but you need need to manually remove and rotate the bezel. The NAC can be rotated but you have to physically remove the monitor from the cabinet. It's not as bad as it sounds and can be done in about ten minutes. The advantage that the NAC has is that the monitor/chassis is in a mouting frame which protects the monitor and so it is much easier to 'pull' if you need to do any work on the chassis etc whereas the E2 doesn't have a frame and so it is harder to remove if needs be.
I've not had an E2 but I have been told that the build quailty on NACs is better than E2s
They are pretty easy no move about. All the common candies I know have wheels on and they will fit though most doorways.
Your best bet would be to head over to
www.arcadeotaku.com and have a look around. We have a ever growing wiki [
here] with lots of good information about various cabinets, hardware, games and there is also a beginners guide which may be of use.