This is why we need polls on here, just let everyone vote...... Go with the 870, more aftermarket parts available....solid gun and should last you a lifetime.
You wont go wrong with either one. If it was me and I had the money, I'd buy the brand new 870 with the thumbhole stock. I just think they are sweet looking guns and have heard good things about them. I have had my old 835 for 11 years and killed a ton of turkeys with it. I wouldnt part with it for all the money in the world though.
Both great guns. The only thing I personally have against mossberg is plastic internal pieces which broke in my buddys 935 last year. Dont even know what it was that broke.