In my experience a 3.5" 12 gauge shell makes a well built 338 Win Mag seem like a [beeep] cat on the shoulder in comparison. Kinda' like the difference between a sharp whack and a hard push.
In my book, if I had to, I'd pick a 338 Win Mag as my one rifle simply because it is a very shootable cartridge in a well built rifle for anything you might encounter short of a trip to Africa.
But to be fair, in looking back at the picture, a boat paddle Ruger of any decent caliber has never been known as being friendly on the shoulder or the face. That combo with the 338 Win Mag cartridge is like putting highway tires on an Indy race car and expecting good results.