I say you do the right thing and watch them both! They are the same in ways, but almost two different animes lol. It's been a long time since I've watched them but it feels like they both have equal watching value on their own.
I have yet to finish Brotherhood, (on episode 8) but, yeah, seems a bit rushed. I've heard it is until around episode 12-13, which is when the story departs from the Full Metal Alchemist series. FMA was pretty good, the ending is confusing and anticlimatic.
I could not even watch Brotherhood, it was a big let down for me. Specially after having seen the original.