don't listen to them. If what you call 'audio engine' is about mixing & outputting sound, then there's no magic, it's not analog, it's dead simple & all sequencers will do that the same way.I am thinking if I buy tracktion I can afford a nice new microphone. But if the audio engine is not as hot as the one cubase uses I might be better of with my old mic and cubase. My speakers are shit so it is hard to tell but Fruity seems to have the same audio quality to me as cubase does. Is this right. Do they sound different?
I'd like to agree with you with "Fruity seems to have the same audio quality to me as cubase does", but honnestly, they will all mix the same way. What can be different are equalizing, compression or other included effects, but you're not forced to use them.
Plugins might not work as well in all hosts, but they will always have the same 'sound quality', in all hosts.
& it's not a matter of faith, it's just math. Mixing signals is A+B. A+B is A+B, it's a simple addition & there's no reason for a host not to be able to add 2 things.
There are things that can matter, but not in what you're calling 'audio engine'.
This won't prevent people telling you that their VSTi's sound better in some hosts than others, though. But when it's in favor of FL, better surf on that rather than complain