Do you find it more difficult to face a team with a variety of types, or a single-type team with a variety of coverages?

I thought single-type teams were easy to deal with, and then Radical FireRed came along and drove me crazy with every gym leader battle, making me want to quit the game. Obviously, it depends on the type, but even so, I feel that even a well-built single-type Bug team could wreak havoc on an unsuspecting player.