Depends on the bike for me...my enduro bike is heavier, I'm not racing it, and I'm riding steep terrain at high elevation on it, so 30t paired to a 10-50.

My XC bike is currently running a 34x10-50...if/when I go to Sram Transmission on that bike, it will have to run a 10x52 cassette, so I'm even thinking about going to a 36t chainring in that case.