I've got an 870 Wingmaster which is from the 1970's. It was given to me about 20 years ago by my uncle. Through the years there ha been a few small spots of rust, but they all happened while in storage. I probably could have used a heavier oil when in storage and not have the rust. Regardless of the small rust, the 870 is my favorite shotgun of all time. Don't know what the quality of the current Walmart offering is, but the one I own is excellent.
I just got done running about 300 rounds in my Beretta Xtrema II this afternoon. It's a semi, and I can shoot it one handed, like a handgun due to the low recoil. It also has a great Aquis coating to eliminate rust. Aside from some of those features, I really think my 870 is a better shooting gun. I would think with the popularity of the 870, somebody you know has one and could let you try it out. I personally would try and find an older model, as I do believe the metals were better, the older you go.