Farscape has more of a Star Wars (OT) space swashbuckling adventure feel. In fact I've always felt Farscape is probably the closest i've ever seen to a star wars tv series - not in terms of plot - but just the feel. genuinely exotic aliens, frantic hallway chases with blaster fire going back and forth, infiltrations, sieges, galactic empires, on the run, etc.
B5 has more of a political DS9/(nu)BSG/ST feel. A lot about diplomacy, political allegories, interactions between different races, wars, etc.
I'd watch the first "regular" episode of B5 on Hulu (Midnight in the Firing Line). It's actually a pretty good tone-setter, even though the main story arcs aren't introduced yet.