I'm in a position where all I have amp-wise is a 10-watt practice amp and a really big 50 watt combo. In the next few months, I'm going to start playing in a worship band weekly (in a small to mid-sized auditorium) and don't know what the wiser choice would be: a Gallien-Krueger MB115 or SansAmp (just the Bass Driver DI). I could actually practice with the amp at home, but the SansAmp would make playing live so much easier. Which would you go with in this situation?
Well, I'd always go for increased flexibility. You'll likely have situations where you'd like to play but can't (or won't want to) go direct to the board. And isn't the MB115 a neo? Those things are really light, so not a big deal to tote around. The SansAmp is certainly useful, but obviously limiting.
Not much to go on there. At a guess, the church has monitors but no bass amp? At a pinch the 50W combo should be ok for monitoring yourself, and more than fine for practicing at home, making the DI the way to go. If there are no monitors for bass at the church then you'll need more horsepower as well as a DI. I don't know if the GK has a DI.
If you like the sound of your 50w combo and don't mind the carry, get the Sansamp. If you want an amp with a little more spl capability, a lighter carry and built-in DI then consider the GK. The GK has classic GK voicing, but can be EQed to near flat if desired.