Well, opinions on the Fishman are very mixed...
It seems that most players don't like it.
I've owned two of them, and didn't like them either.
It picks a lot of string noise, being mounted so close to the strings.
I had a few Underwoods and liked them very much.
I've heard nothing but good comments about the K&K Bass Max.
I'd go with it.
But in any case, I strongly suggest you get a preamp, to act as a buffering device between the very high impedance of the piezo pickup, and low impedance input of most amps. Impedance mismatch results in thin, shallow tone with no bottom end.
K&K has a small preamp too.
Bob Gollihur is a good contact for them.
mailto:bob@gollihur.comhttp://www.urbbob.com