Best of luck trying to mouse on-screen faders around in the middle of a gig........

Unless your laptop screen is touch sensitive, what's the point of a virtual slider? You still have to move it (and probably two more at the same time!) and get your hands back to the keyboard accurately and quickly - not at all easy with a trackpad or mouse.

Get a keyboard with real faders. So much the better if they are motorized, but even without (PA-1X, G70 etc.), it's WAY more effective than a mouse..........