It all end up on the indivudal and how well he handles his cycle. I have seen several friends run dbol onlyh, get big and strong and two months later you can barely tell that they did roids.. why? because Dbol cycles only suck. Having that said, somebody experienced with a decent base will probably do better, but that person will probably never run dbol only.
IMO Dbol only is usually run by novices that will most likely loose most of their gains regardless. Dbol is just idiot proof enough that you will gain weight ( water) even if your diet and training sucks
I hate that shit because my hair falls out, because it gives me gyno and because I simply do not like that much water retention. Tbol rocks compared to that.