The Winchester guys always point to the fact that the guns were made with state-of-the-art (for the times) chromoly forgings, which is true. They skip over the fact that it is tough to get solder to wet that steel properly and model 21s are perhaps the gun most likely to suffer loose or popped ribs. Happens all the time.
Per the American habit of taking something that worked well (12 gauge 2 3/4" cartridge) and making it bigger, not better, the Model 21 might fair better on a steady diet of ammunition doing a howitzer impression. But, for use in what most would consider "game gun" type configuration, the 21 is a disappointment, invariably heavier, less well balanced, and with the asthetics of pickup truck. I suppose if one were going to shoot doves by the thousands in Argentina, without a lot of walking about, a 21 could be ideal. But, I can't imagine a grouse/woodcock hunt where it would be superior to, well, lots of other things out there.
There. Klunk, in spirit, lives.
Best,
Ted
