They're different amps, despite the name and roughly similar output rating. Tweed has more upper mids, lower clear headroom ceiling & more compression at clip. Bf has a more "scooped" midrange & a much tighter, raspier "crunch" at clip (which won't set in til the amp is really pegged). Bf is the louder, cleaner, more "neutral" option. Much depends on speakers, too: mating up a bf head with the same 4x10 alnico array found in the tweed is going to produce a warmer tone with looser bass than mating it with the ceramic 2x12 bottom they came with from the factory.