Aulos 511 symphony or Yamaha 304bII?
And why?
I suspect this is one of those things where you’d have to try both to see which you prefer, or, barring that, pick one and you’ll likely be happy enough with it.
In the Yamaha vs. Aulos (and sometimes vs. Zen-On) debates I’ve seen, both have their fans who insist one or the other is better, and then there are the people who say both are great.
I doubt you’ll get many respondents on these forums, but you might get more, & better, info here - https://recorderforum.com/forum/
Both recorders are good (good intonation, good tuning, good balance between the registers). My Yamaha has harder keys than my Aulos, therefore it’s less pleasant to play in the long run. The Yamaha sound is slightly “reedy”, the Aulos sound is slightly smoother, in the low register especially. All in all, I think they are equal in quality.