i own them all and many more. imo s-gear2(scuffham) is over rated, i haven't fired it up since the 2.53 update maybe 18 months ago, it just doesn't sound or feel that good to me compared to others.
guitar rig, owned it since 3, own the latest, never use it, imo sounds like crap, cleans ok but overdriven, distortion, forget it, there are much better
amplitube, i own everything available for it, it's not bad, gets more use than the above.
bias fx pro, own it and bias amp pro, in my opinion a step above the rest
don't forget revalver 4, it is right up there, and with the release of the act stuff, especially act combo and act combo presets, oh what the hell even the act input modules, it has risen to the top for me (or equal top with bias stuff)
those act combo presets sound awesome. (you got to profile your guitar and a few other things, easy as, and results are awesome, imo of course)
for a long time i never touched revalver, it was all either bias fx pro or bias amp pro or sometimes th3 or amp 4. then the act combo thing came along and i gave it a whirl, and as they released more act presets (basically amps) i just began using revalver more and more, and not just the act combo side, even just the 'normal' stuff, now i pretty much use it exclusively, with the occasional switch, wish the stomps and fx racks were up there with bias fx pro though, but hey