Well, since we don't get to pick and choose, normally, I'd say anything VMC is fine. A bit better than marginal VMC for aerobatics.
But the best memories I have are from those crystal clear winter days just as a cold front has passed through and dumped a lot of snow on the ground. Magic.
(And extra sweet since flying is also a reward for spending an hour outside in bitter cold trying to get the plane clear from all snow and frost.)