I voted MERP. But if I were to run a Middle-Earth based campaign, I would use MERP as the basis, but also use RMC, RM2, RMSS/FRP to update and extend some of the material in MERP.
If memory serves, all of the spell lists were limited to tenth level?
However, since I no longer possess any of my MERP material (lost in fire), I would have to say I would use the RMC/2 systems since it was on those systems that MERP was originally based. Was it not? If pushed, I might would port it into the RMU system.
rmfr