Ok, I have done a fair amount of research on these mirrors and this is what I have come up with.
Below is the official BMW wording of the options any mirror can have:
EC = Electrochromatic (auto-dim)
Radio = Radio-wave remote control (315mHz amp./antenna for your key fob, only needed for convertibles)
LED = Light-emitting diode for alarm system (clown nose beneath mirror for cars w/ alarm, it flashes when the alarm is active)
GTO = Integrated remote control/garage door opener (homelink)
FLA = High-beam assistant (not offered on 1M)
Compass = Digital compass display (self explanatory)
ETC = Electronic Toll Collection (not offered on 1M)
TLC = Out-of-lane warning (not offered on 1M)
There are a ton of different mirrors with combinations of the above options. While I was searching on eBay for a mirror I kept looking for a mirror that had EC/LED/GTO/Compass. The radio feature (or RC or 315mHz) doesn't make a difference because that is only necessary for convertibles. Verts need the key fob amp./ant. in the mirror because they don't have a c-pillar or roof panel to fit it in like all other cars do. Its usual location is in the c-pillar. Here is an example from an E46:
http://www.bmwgm5.com/FZV_Antenna_Amp.htm
Just thought this explanation would help save some people time.