I've owned a Bongo and G&L's. Directly comparing them they are very simular in a lot of ways, and very different in a lot of others.
Simularities include very extensive versatility, professional quality and powerful easy to use preamps.
The differences are that the Bongo has an 18v pre, whereas the G&L's have a 9v. Tonally, the G&L (although clearly a suped up active pre) sounds a lot more organic than the Bongo, which sounds more hi-fi. The L2000 compared to the Bongo will have wider string spacing for sure. The body of the G&L's are the reason my bongo had to go, it was just more comfortable with the smaller body.
Both are super great basses, and they are definately my top two picks right now. Some other things to note is that Bongo's only come in rosewood for fretted, G&L can be maple. Man I loved how the Bongo had just a tad more oomph and definition. The paint on them chips like a bugger though, have to baby it like a newborn to retain the value with a painted headstock and neck. And the basswood body is soft.