I agree with Vmac here, although I still think comparing MP to SP is fucking dumb.

MP is like a crude and brutal version of SP.
The top replaymaking scene is what we consider the epitome of the game, the flow, the booms and all of that is what we try to replicate even in MP. It's all about effective movement, getting the most power out of any given position and using that power to either crush our opponents (MP) or make the most spectacular move possible(SP).
Therefore what you can do in SP boils down into what you can do in MP.

Besides I think SP is a much better way to start your Toribash "career".
The resources you have availible through other replaymakers replays and various mods are vast, if not limitless.

Again, if you strive to make, lets say, a 4DM boomhit in singleplayer you will eventually get it done because you have an unlimited ammount of tries. It may take a couple hours and during that time you will have learned something about DMs and how the Tori is built.
Using that knowledge in MP can then get you a 2DM hit, maybe even a boomhit if you're lucky.