Another vote for the fantastic Ithaca Model 37, though my preference will always be a 16. Incredible value for money in any gauge, very slick action. For grouse, nothing beyond 2 3/4” is needed. And 2 1/2” shells kill them just as dead (and with less recoil).
And at the risk of sounding like a cranky old git, forget all the marketing nonsense about choke. At the distance you will be shooting grouse, with lead, modern shells and plastic wad cups, you aren’t going to see much difference if any. Concentrate on becoming a better shot through technique and practice. Find a gun that fits you and will become part of you, and which will give you real pride of ownership. Start with quality as your first criteria.
Choosing a gun shouldn't be like choosing an iPhone or a pair of trainers. Many here have been shooting their treasured guns for 30-40 years, which is a pretty long relationship (and longer-lasting than some of our marriages, speaking from experience).
I won't call you a cranky old git, Pinfire, but my early hunting days were with a full choked single barrel 16 G Cooey and the effective pattern tested to be about 8 inches wide at ruffed grouse flight ranges, which is to say 20-40 feet. Hitting a rapidly vanishing bird under those conditions wasn't outstandingly easier than shooting them out of the air with a rifle.