From time to time I find myself in positions where material is even but one player might have six pawns for two minor pieces. Which situation would you prefer and why? Does it just depend on the game or is there an advantage to having pawns rather than minor pieces?

I'd say it would depend on what minor pieces you have left. I wouldn't prefer that advantage if I had to bishops left, but I might not might it with two knights.  I guess theres a lot of factors that go into it, but I would prefer to have the minor pieces.

maybe six pawns would be too much of a workload for two pieces one of them might slip through and promote and that would be decisive

Depends on where the game is and where the pieces/pawns are located. If the pawns are scattered around the board, or the pieces are unharmonious/blocked in, then it would swing my decision. If it were a Knight against three Pawns, I would want the Pawns in an endgame. I've sacrificed a piece for three Pawns a few times before, but it was mostly compensation, and to displace the King, so I had other motives.

All in all, hard to say!

so would a bishop vs three pawns be better than a knight vs three pawns? I know you can control all of the pawns on the same diagonal if you have the right coloured bishop.