I thought the VT Bass / Flyrig was much more usable than the amp sims in the B3 / B1on / MS-60B. There are tons of people happily using them live though, plus the amps in the B3n are a generation forward and reportedly much better then the previous gen. There aren't any decent demos of the B3n I've seen that go through the amps in detail though. You could very well find one in there that you prefer to Tech21.
I think the best solution would be to pick up a B3n, then find an old VT Bass pedal since they are fairly easy to find used. With any luck you should be able to get those for the same price as the Flyrig. If the Zoom wins on the amp sim front, sell the VT for the same price you paid. If you prefer the amp sim in the VT, either keep the pair and use them together, or trade for a Flyrig if you really need that more portable form factor.