Miller,
Mom was born on March 31, of 1938. I hope your health is much better than Mom's, while she is still here and sharp as a tack, she won't be doing any grouse hunting, 26" tubes or not. I like barrels anywhere from 25" to 28", don't have any over 28" at the moment, but, I had 30" on a MacNaughton boxlock, and a Western Arms, both 12 gauges, back in the day, and I liked them, too. If the gun is proportional, and handles well, barrel length isn't a huge concern to me. This Ithaca Nitro, in 16, handles above pay grade.
Every time I see a model 21, I think the same, exact thing. I blame Klunk for pointing that out. There were a lot of good ideas that started out on the Nitro that ended up on the NID, a solid double that is worth more than a Nitro, but doesn't shoot any better. +1 on having a 16 that is up to whatever ammunition I can stuff in it.
Can't say I'll keep it forever, but, it has a slot in the safe today. Selling a gun of my own is a really rare thing for me, however.
Best,
Ted