You have picked a controversial subject.
No one doubts the worth of the 28 for birds the size of quail, woodcock and doves.
Grouse are bigger birds and some think the 28 is fine for them, others don't. All you can do is try it and see.
I have learned to respect both sides of the argument as it seems unresolvable. Kind of like the "Is the .243 Win, gun enough for deer" question. Marginal and works for some, not for others.