I've owned and tried a LOT of these low to mid tier 6'ers. This is just my experience with these brands/basses and I do no intend to represent everybody else's experiences. So...my $0.02:
ESP: B and D series. Tight string spacing, QC has been a bit all over the place. Wide flat/thing neck which I like. "Meh" tone IMO.
Schecter: Largely "fine" in my book. Tighter string spacing, sounds fine, divisive aesthetics, QC is decent overall. The very definition of "Ya, it's nice."
Ibanez: SR series has tight string spacing as well, usually pretty good QC, and tend to have THAT Ibby tone. Which some call versatile, I call boring. The BTB's are the same story, but a have wider spacing and have the 35" scale which tend to have little more clarity down low.
Spector: Again with the very tight string spacing. Necks are very middle of the road. Not too fat, not too skinny, not too glossy, not too raw. Has the EMG sound going on if you like that (mostly.) QC on the Legend seems to be pretty hit and miss and the preamps aren't great, but mid tier and upper tier line are lovely if you can find a nicely priced used one. Some people like the Tone pump pre's some hate them. Rebops and up are undeniably nice basses though.
MTD Kingston: Wider spacing. Great QC. Wide but thin neck (kinda like the BTB.) Tend to fall down a bit on the electronics. Darker pickups on Z line. Overall a very nice instrument though.
Warwick: Variable string spacing is nice. The newer Rockbass line can be quite good. QC seems to be hit and miss on the new ones. Thinner neck than the GPS or German made stuff. Main difference is body/neck wood and preamp. The preamp being the real weak spot on the RB line. Still has the majority of the "Warwick Sound." As far as the higher end Warwicks, I don't know that you'd be able to find a used 6'er in that price range, but fit and finish are certainly top notch. Neck profiles have really changed over the years. I'm not an expert, but I *think* that they were pretty chunky during the 90's and early 00's but more recently they've slimmed down quite a bit.
Carvin: Can be found used for great prices as Carvin tends to have low resale value. Usually very tight string spacing. Fit and finish are known to be pretty great. Sound/feel is largely dependent on the options the original buyer chose...I've played a few and while they felt like quality, they've have indeed varied greatly in the end result...which, I assume, is what the original owners wanted.
Had a chance to play a Yamaha TRB6 a couple times. I was impressed. Sounded great, played great, felt great, but also felt very big. Big body, big neck, heavy. Similar to the BTB but a fatter neck IIRC. Still sounded killer though. Used prices are all over the place.
Have not had a chance to try any Cort or Tune stuff nor a Brubaker Brute. Though I'd really like to.
I think that's all for now. I'll be waiting for people to yell at me for something.
