I don't have an 835 or an SXP, but I have had a Mossberg 500 I bought in 1980 that's still going like new. In 35 years I have had to replace only one part, the trigger guard, which I broke myself, no fault of the gun.
This 500 has came with an 18" cylinder barrel and wood furniture, I added a Polychoke later and hunted with it like that for years. Over time I have acquired several other barrels, and it's the only gun I have ever spray painted, more than once. It's been rained on, dropped in mud and once went over the side of the canoe.
When I replaced the trigger guard last year I stripped off all the old paint, went over all the metal with cold blue and Aluma-black and added a set of Hogue Overmolded furniture and it looks and shoots like nearly new.
Does this sound like a gun that's been babied? But it just keeps on going...
The 835 is the 500's bigger brother and is even better built. I presume you know the difference between the 835 and the SXP (and the Mossberg 535) is the oversized bore on the 835 smoothbore barrels.
Mossberg uses a barrel with a 12 gauge chamber leading straight into a .775" bore, that's the 10 gauge standard vs. the normal .729" 12 gauge. It's supposed to give better patterns and velocity, and the guys that use them and the 935 auto seem to really like them.
Oneounceload is dead on: when shooting heavy loads you will come to appreciate the extra couple pounds soaking up some recoil. My 500 runs right at 7.5 pounds now and 3" duck loads will get your attention, even with the excellent Hogue recoil pad and synthetic stock.
One last point, the 835 is 100% American made and the two times in 35 years I had to use Mossberg customer service they were excellent and really took care of me, the last time so well that I shouldn't post the details here. :wink:
The Winchester SXP is made in Turkey. Nothing wrong with Turkish guns, I and friends own several, but it might make a difference to you, and parts and service may not be as easy to come by.