First, I'm a dabbler not a URB player -- I do have a BugBass, so here goes.
Mine is the original Original Model BugBass, which had a metal bridge plate. I don't believe that the newer models use this method.
I've got an old set of Corelli 370's (Solo) on my 1998 original BugBass. They've been on there maybe 5 years, were used when I got them, and still sound pretty dang good! I'd say modern perhaps -- certainly not old and "thumpy". Good projection and cuts well. Medium bright to start, but are mellowing nicely.
I don't play the 'Bug much, so I can't testify how well they'd last for someone who plays a lot.
I will say that since the Corellis are Solo gauge strings, it was easy getting used to them, since I mostly play 5-string EBG.
A question: The pickup on my Bug' is incredibly sensitive (and HOT!!!), especialy to string and finger noise. Have you noticed this with yours? IIUC, this pickup is a K&K Bass Max but I believe that Azola has gone to a different model on current production. I don't hear it over the band, of course, just when I'm sitting around playing. Could the pickup be part of your concern?
Hope this helps!
dcr