In V20, my favorites were the Tremere. Thaumaturgy was completely broken, and while I didn’t try to make my PC too powerful, I stood out. Plus I’m a fan of their whole hierarchical, cabal-ish, seeking knowledge thing.
V5, probably Toreador. I’ve had so much fun playing my current one. In Night Road, I’ve played all of the clans but I one I’ve played the most? Lasombra. I really like the Lasombra PC’s backstory, the MC’s sire, the fact Oblivion unnerves even Kindred like Julian and Lettow, and the fact people aren’t used to playing nice with one.