Some of the other differences: With an overflow you typically have to work harder to get the flow the first time because you have to empty the air out of the tube from the tank to the outside overflow (using a tube). Sometimes this also gets air pockets that limit the flow. Also, with an overflow you can't put the tank all the way against the wall, you have to leave room for the overflow.
I've never had a pre-drilled, only and overflow and I personally didn't like it. I ended up getting rid of that and went with a canister filter.