get both
you'll find that you can use them for a wide variety of things. i recorded
my martin d15 this weekend (with someone else playing) using a pair of 603's in close and the B1 about 4ft away. it sounded HUGE. i wish i could get that kinda sound when i'm recording myself, but i'd need a clone to tweak everything while playing. ;-)
i've also used the 603's as overheads for my drums and as "room mics" while recording my band's practices--both with nice results.
The B1 has seen time as a snare mic (again, sounded quite nice and got plenty of the hihat sizzle, but not too much), and also as a guitar cabinet mic. In fact, the b1 turned out such a nice sound on that fender tweed blues junior that i'm gonna pick up another one so i can leave it on there permanently. talk about a "sleeper" application for that mic. i've always used 57/58's for cabs.....but the detail off the b1 was far superior.
needless to say, if you get a pair of 603's and a pair of B1's, you'll have a pretty strong starting toolbox. hell, even one of each will increase the quality of your recordings considerably--neither of them are "one trick ponies", and you'll be happy with both.
ymmv,
wade