Tbol doesn't cause water retention so the gains are more keepable. If I'm not mistaken tbol is a derivative of dbol. I've never tried it but everyone on this board seems to love it.
I don't particularly care for dbol...makes me lethargic and bloated. I do always end up running it for the 1st few weeks of a bulker though. The rapid strength and weight gains are insane...no waiting around for the injectables to kick in.
It all comes down to personal opinion, both drugs kick in quick and will produce good gains. If you're looking for all out mass go with dbol, if you want quality gains go with tbol. Either way I'm sure you'll be happy. Good luck bro.