The Twin Reverb is an Awesome amp...... Very Loud and very clean. So if clean and loud is what you want its will be hard to find a better Amp. The Reverb in a Twin IMO is still one of the best available. The size of the springs adds a lengthy decay to the reverb which is beautiful. The Twinn has 2 12" speakers and is rated at 80 watts.
The Bassmen is primarily the same circuit that the original Marshall Bluesbreaker was based on. The difference is really tubes. I am pretty certain that the Bassmen is 40 watts with 4 10" speakers. No reverb, but absolutley beautiful tone. For me I need reverb.
The Twin in most cases is going to be to loud. The Bassman will be more manageable. The Twinn with 24" of speakers witll move less air then the Bassman with 40". I think the Bassman has a stronger bottom to it than the Twin.
Both of these Amps can be difficult to use in some clubs. I prefer the Super Reverb over both of these and in certain situations(small clubs) The Deluxe Reverb is probably one of the best Amps for all around use. The major drawback to a Deluxe (22watts) is they have very little headroom by comparison to a Super, Bassman or Twin. Out of all these Amps the Twin has the most headroom of them all.