I switched to DSL a few years ago and, quite frankly, I didn't notice any real difference in game play. About the only thing I really appreciated was my 56k modem was screwed up and wouldn't would drop download speeds to next to nothing after a minute or so. So, when I'd want to come up for a quick few fights, there'd be a new update of one kind or another that might take 20 minutes or so to download. Now it just takes a few seconds, if that.
I'm sure if I switched back to 56k after using DSL I'd probably notice some difference, though.