After a full day of shooting, the 1100 will beat you up a lot less than an O/U. Especially if you ever use more than a 1oz load. A 1 1/8oz high velocity load, like you might use in sporting clays is harder on you in an O/U after 100 to 300 shots. (assuming 12 gauge here)
Also, if you buy a used a 1100, you can get a lot of gun for less. If you buy a new gun, just like you described, you will probably have it for life. I bought my first 870 when I was 14, and 25 years later, I still have it. Back then you had to add the middle bead.
The Russian guns are nothing like Remington. The rusky O/U's I have handled seem tight in their action. You may end up having to polish the action to make it smooth so it won't wear you out. I have polished Beretta's just to save time on breaking them in. Of course I am old and have many injuries so my shoulder and elbows are not as tough as yours. Also, over many years of absorbing recoil, there is nothing wrong with cutting back wherever you can while you are young. Same principle as wear hearing protection today, hear tomorrow.
When I was 14 I wanted an O/U! 30" used Beretta. My boss at the gun club used it to shoot cows in the corn. He would not sell it to me.