Same as redir,
soundwise there won´t be any drawbacks.
Which Fishman are you thinking of ?
piezo, soundboard transducer, magnetic or mic
I think a combination of a well placed mic and some sort of direct sound always wins in a recording situation. You have a lot more possibilities when mixing.
And you might use effectpedals for the guitar :-)
Here is a clip of different pickups:
Might not be a good represantion cause I used different eq settings for each channel.
Maybe it will help you:
http://www.polyphon-recording.de/pickups.zip
Played on the same guitar Breedlove Atlas Solo
1. Fishman rare earth mic only
2. K&K pure mini western transducer
3. Fishman rare earth magnetic only
4. LR Baggs piezo
5. 1+2+3 together