An interesting topic & I'm surprised it hasn't drawn more comments.
People seem to either love the 21 or don't like it at all. One of the English gun writers (Geoffrey Boothroyd possibly) referred to the 21 as "Truly Ugly" which I think is a little extreme but the 21 is a long way from the most handsome boxlock I've ever seen. I would call it solid & purposeful looking sort of like a 32 Remington/Krieghoff K80 O/U would be described & like the 32 Remington/Krieghoff K80, covering it with lots of engraving & or "gold chickens", doesn't IMHO improve the looks over that of the basic gun in most cases. I like some of the custom aftermarket engraved guns that are done with a little restraint much better than I like the factory pattern highly engraved guns.
The 21 has a reputation for strength & durability due to the long action bar & the type of steel used in it's manufacture but as Ky Jon has said in his comments the 21 is on heavy side & this is especially apparent when compared to English & European game guns of the same gauge.
To me most all 12 ga 21's are too heavy to be considered for use as an upland gun but they make an excellent clay target gun for the few of us who prefer a SxS for clays & for those that prefer a single trigger the 21's trigger is one of the better ones made.
The 16 & 20 ga. 21's however do make very nice upland guns as their weight is reasonably close to that of a 12 ga English game gun. I especially like the feel of most 16 ga 21's & the weight is close to perfect for shooting 1 1/16 or 1 1/8 oz of shot.
