You are absolutely right - personal reasons.
But in case of every Mig21 user, OB is more or less mandatory - you cannot see out of the cockpit in release version.
Unfortunately the best server fot this plane is just not in OB (ACG cold war).
If the versions are again on the same level, and maybe the Mig just got the mandatory updates, maybe i'll go for release version, just to be on this server.
Otherwise I'll need some new server to fly this thing in a fitting setting ....