For none of u have tested this out yet, I just have. If this has been posted, then I'm sorry.
During Vs Mode, I tested 2 monsters and each handicap. They are Mogli(mogi, 600/999/1/999/999) and i used headbang, which did on 5/5handi, 130 dmg. The other guy is Seldukai(Zan? 695/999/6/999/999) and i used rising rave, which did on 5/5handi, 250 dmg. Here are the results of each handicap:
6/4 adv to Mogli:
Mogli does more dmg, headbang 150 dmg. Seldukai does ris rave, 200 dmg.
7/3 adv to Mogli:
Mogli does more dmg, headbang 170 dmg. Seldukai does ris rave, 180 dmg. Mogli increased accuracy, just slightly.
8/2 adv to Mogli:
Mogli does more dmg, headbang 195 dmg. Seldukai does ris rave 140 dmg. Mogli has slight change: ++accuracy.
9/1 adv to Mogli:
Mogli does mroe dmg, headbang 300 dmg. Seldukai does ris rave 100 dmg. Mogli has great change in accuracy: all bars were full.

All attacks were done at 99 guts