Once you get past the first 15-20 episodes or so (I forget what the number was), FMA:B was in a lot of ways the better-paced show (egregiously long Final Battle sequence aside) because it didn't have to hang around with filler episodes waiting for the manga to keep pace. I think Brotherhood also had the more satisfactory conclusion in a lot of ways. So if you found the first one too dark for your tastes, it's probably just as well you didn't finish it.