choose a small elite alliance and end up with 10-15 players out of 40, then try and recruit or become too elite. choose a big alliance and get stuck with boring internal conquers, ghost cities and teaching as a second job.
the fact that mra's have to defend a lot is not surprising since they often accept nearly anyone, then have to support them. the fact that they get targeted by multiple alliances at once makes the elite alliances who team up with other not that much different in size.
in a perfect world without inactivity, somewhere between nat and nr in size would be ideal.