I absolutely LOVE the ergos of the BPS and despise the 870 since I'm a lefty shooter. The Browning seems to fit me well right out of the box, too. I don't own one, yet, a shooting buddy does and it's a wonderful, well built shotgun and I plan to get one in the future with a camo finish on it, someday. It'll be a 3.5" gun or a 10 gauge, not sure yet. I will waterfowl hunt with it, mostly geese, but also ducks. I sorta think of my Mossberg as a budget BPS, tang safety, good lefty ergos, FAR superior to any 870 for a lefty. But, the BPS is one slick pump gun for sure. I've used the 37 Ithaca in the past, very nice gun, but not as lefty friendly as mentioned above. Crossbolt safeties suck. Even if I could reverse the safety, I'd rather have a tang safety. It's just more natural to me, probably due to the fact that my doubles have it and I'm used to a tang safety on shotguns and working a safety with my thumb on my rifles. My Remington rifles and my Savage 110 don't have crossbolt safeties. Why is it that most shotguns do? It's a cheap way to design a safety, I guess, but the Browning isn't cheap. It's a step up over your run of the mill Wingmaster, let alone Express.
Oh, I'd take the cleaning the action comment with a grain of salt. I hunt in tough, salty, wet environs and I have learned, though experience, to strip the thing at the end of the season for a thorough cleaning. If all I did was dove hunt with it, I might not even pull my Mossberg or Winchester apart, but hunting ducks in the salt marsh requires better hygiene.