The 590 is a good solid gun, if you prefer it to the 870 then it's one of the best alternatives available. As to Hans Vang, he has an established and well earned reputation for doing good work. His internal mods to shotgun barrels do indeed work in improving patterns, I'd as soon reserve judgement on the porting but lots of people swear by it. I don't own one of his barrels, btw- I've always settled for extending forcing cones and havng choke tubes installed. Keep saying I ought to try one, but haven't so far.
lpl/nc