I think you mean the Mossberg 835.
Both shotguns are excellent, the mossberg 835 is a 3.5" chamber so you can use from 2.75" shells to 3.5" shells, the Remington is 3". If your going to do turkey then the 3.5" chamber may serve you better. Do you know if they both have a rifled barrel/cantilever scope mount? I know the Mossberg does. I own the 835, I don't use it for deer anymore, just to heavy, but I use it for turkey. If you go with the 835, and use slugs in it, DO NOT use 2.75" or 3" shells, you must use 3.5" shells for liability reasons. As far as scopes, the 3-9x40 is great, but I wouldn't use a Tasco, no offense but they are cheap and garbage, remember the 12ga. kicks/recoil like a mule, you need a scope that can take the pounding, look into the Leupolds, Nikons, or if you don't want to spend alot, look into the Bushnell's Trophy Series scopes.
Also the Mossberg 500 combo is there version that competes with the Remington 870, you can find the Mossberg 500 combo on sale at DICKS for like $280