With a Trace (and in my experience with a Handbox, Genz, TecAmp, GK and various others) you can set your EQ with for example a P bass, but then if you switch basses mid-set to say a Stingray or Sandberg you still had your core sound but the P would sound like a P and the ‘Ray would still sound like a ‘Ray etc, etc. I found that with the Ashdown I could tweak the EQ to get a great sound, but if I then switched basses I’d need to mess about with the EQ all over again. The EQ seemed very specific and precise to the bass going into it. Probably a very good thing to some but to me seemed a bit of a faff.
As I said before there are lots of people far better placed than me who love them to bits, so each to their own.