Only a personal opinion but some people seem to change their gear more often than their underwear!
I have 2 Markbass heads that i've used for the last 4 years (LM11 & LMK) & think they're great, Absolutely perfect for my requirements & have a very clean, true tone.
And there-in lies the problem, i think, for some people.....
My MB tone is fairly 'transparent' as i rely more on the individual tones of my basses...
i.e my Alembic sounds like an Alembic, my Warwicks have 'that' growl etc. if that makes sense?
I'm not suggesting that others are playing basses of 'lesser quality or tone' but, you kind of know what to expect when you plug a 'Precision' into a SVT (Bad analogy i know but you understand what i'm getting at?).
One thing that took me a long time to understand was personal tone, everyone's is different, even using the same gear as a 'hero', what works for one player sounds like a wasp in a dustbin to someone else.
Also there are a few manufactures out there now making these small/powerful heads, each with a different tone i.e a G.BENZ shuttle sounds different to a Eden to a MB etc with various extra functions such as comp/limiters, valve inputs, 3 band/4 band or graphic eq.
I suppose it's what works for your bass & tone (whatever sound that is?, in your head or through your choice of cab)
Other than that, i think we're all a bunch of fussy b*%$+#@'s with tone paranoia, when half the time we just need the one big volume knob on our amp to hear ourselves over the rest of the band!