I own a Beretta 391 Sporting which is the same gun as the Teknys although not as fancy. Mine 391 is a back-up gun for my o/u and my waterfowler.
I shot a Benelli SuperSport for a day last summer and it's also an excellent gun and here are my observations:
The Benelli kicks more even with their hi-tech stock. Their system however is simple, robust and easier to clean. The Beretta is harder to clean but in my experience will run 1,500-2,000 rounds before it needs cleaning something that couldn't be said about the Remington 1100 that I once owned.
Benelli suggests using 3 dram 1-1/8 ounce loads for the SuperSport while the Beretta is very tolerant of light loads. Mine will shoot 7/8s ounce without hestitation.
Because my semi does double duty the Benelli's shiny receiver isn't something I'd take into a duck blind. The gun is also ported which can make one very unpopular with other hunters or guides in your blind.
The Beretta LOP is 14-3/4" with the longer recoil pad. Benelli tops out at 14-3/8" which is too short for my liking. Both guns have a shim system that allows you to adjust drop and cast which is a very desirable feature.
I'm not about to trade my 391 for a SuperSport but I wouldn't feel too hard done by if I'd chosen the Benelli instead. Benelli makes a matte finish version of the SuperSport called the Cordoba and it would be my pick even though it also has a ported barrel. If I were to buy one and I may at some point, my duck hunting buddies will just have to bring ear plugs.