The main issue I have w/ bass samples is mostly that, though I do manage to play keyboard, it's just not as immediate to me as it would be to just grab the instrument and play the lines.
In terms of sound, Scarbee is great. Usually a blend of the clean sound and a bit of SVX goes a long way, sonically.
But it's really more a matter of speeding up the creative process, because I realize that not only playing bass via the keyboard isn't as intuitive and quick as it could be but it has also become a thing which I dread, because it feels like it's stalling the whole process. Writing bass lies would just be easier to accomplish on the actual instrument.
Once I'm done writing, I'd have no problem going back in and editing, adding little details and fine tuning. Anyway, once the basic track is cut, I can always send it to one of our bass playing fellows who'll be more than happy to assist.