I strongly prefer directional keys. Control scheme feels like much more of a preference thing in MO2 than in 1. I wouldn't include "Use experimental" as a tip unless you just want more people testing the experimental. You'd be better off explaining the advantages of each.
Some great advantages of using movement keys rather than mouse:
1) The keys will never give you an attack you weren't asking for, just because your wrist wasn't perfectly aligned. A key is either pressed or it isn't.
2) You don't have to swing your head around to cock back a swing, disorienting your aim, and possibly allowing an opponent to sidestep.
3) You don't have to drag your mouse one way, and then back the other to drag your swings, you can just skip right to the way you want it to go, which is faster by default.
4) For low ping fighters, opponents can't watch your turning to guess which way you're going to swing, because you don't turn, you keep your eyes centered on them, which is more intimidating for sure.
4.5) Keeping your eyes on your opponent will only become more important if/when blocking arcs are introduced.