I've had all three and personally I'd stay away from the Schecter, not bad but not great either and no resale value. Of the two remaining choices I'd look at their cheaper alternatives.
For the Fender I'd look at the Squier line, some really nice sounding and looking basses there for half the price (or less) than a MIM or American Fender. You can get a really nice one for under $500. A few months ago I landed a new Squier Jazz 5 for $250 and it just killed the MIM and USA model when it came to tone and feel.
For the Musicman I'd look at a used musicman SUB bass (on ebay all the time around $500). You can get an active model in 4 or 5 string and it plays just as good and sounds exactly like my vintage Stingray. I like the 2 band preamps on the stingrays but some like the 3 band preamps. Try both, they are very different!
In either case always try before you buy if possible, especially on the Fender products, not as much consistancy from bass to bass. The Musicman products seem to be much more consistant from instrument to instrument, so if you can't find a local SUB just try any of the 2 band Stingrays to get a feel for tone and playability.
Someone else mentioned G&L as well. I've had that also. Hard to find one in a store to test but they do sound and feel nice and are in the same $500 ballpark (Tribute model) as the others I've mentioned. But this is one that should be played before buying, not because of the consistance, they're built fantastic. But because of the tone. I ended up trading mine in for a Stingray 5 because I couldn't ever get the sound out of it that I wanted. Don't get me wrong, they are very flexible basses with tones of tones and sound options, I just couldn't find more than one setting that I liked and that was the passive setting.
Good luck