Assuming you're talking about using one of the global velocity curves that you can select on the controller itself, as you move up in the numbers, it becomes more aggressively leaning toward high velocity (so a curve that looks like a hill instead of a valley, sorry if there's some more technical term, I'm not sure). 5 feels straight diagonal to me.
Being a player that likes a bit more expressiveness on the low-velocity side of things, a lot of soft subtlety, I've found 4 to be perfect for me. I can also say that after probably 7 or eight nights of multi-hour playing, I've either gotten very used to the resistance provided by the keybed or it's softened up quite a bit (my guess is a combination of both). Plays like a dream now.
