The super nova is a fantastic gun. Nothing but outstanding quality. Super reliable, no loading/ejection errors like the 870 has so often. Its much lighter than the 870, built better, with better materials, and hence why the gun is many times the price of the 870. Much smoother action, not clunky and sloppy like the 870 as well. If you prefer your gun to weigh a lot, operate slowly and with slop, then get an 870. If you prefer to stay with a years old legacy, of handing over a rusted gun to your kids, get an 870. If you want american heritage, and a wood stock, get an 870. But if you want the best, the lightest, and the work of continuous improvement, get the super nova.
If you are to get any pump, especially to last to give to your children, then get the super nova no questions asked. They will thank you later for getting a shotgun with a good recoil pad and that they can actually lift and shoot before they are grown up.
Just my .02, I am obviously heavily biased against the 870. But when you spend time at the gun counter, you see what is good and what isn't. And yes, I have owned and shot both. I started with a 870, then a super nova, and now a cordoba. If I was to start over, I would have gotten the super nova first.