hawilson, we all have opinions, you will get a good motor with both the ss or ls BackH20. I think if you ask BackH20 Inc., THEIR opinion, they can give you plenty of good info to help you make your choice. The discussion on speed/mods is a little like the shotgun pellet debate- hypervelocity as Rem makes on their newer shells- and the more standard 1400 fps loads- everyone should pattern their particular load/choke/gun to find the "best" pattern; I don't have geese to hunt, primarily divers, so the cheap federal blue box 1 1/4 oz. #3 1400 fps 3" shell is plenty. Your conditions, your typical load, should dictate first of all, if you even need a mud motor. It became obvious to me after a few torturous seasons with a conventional outboard, that running in shallow, hard bottom, weed-choked waters necessitated something else and that became and still is the longtail motor. Not fast, limited because there is no gear reduction (exception: the MB SLT drive), so there is plateau of diminishing returns as far as adding any expensive mods to the motor, because you cannot spin a larger prop, whether submerged or surface piercing, especially when the water level drops. Maximizing the performance is a trial/error thing, each boat hull is slightly different, so learn over time how to arrange the weight/load on your particular boat, from the start you need to be safe and have all the safety equipment. Each mfg.'s prop is slightly different and this will be a big factor, a 25 HP might have a 9x7 recommended but a 9x6 might get you 1-2 mph more.
fowlhabit4, please post when you have run your new BackH20 35. We all benefit from shared knowledge on this site, and we may appear to be "dinosaurs" to the SD crowd, but look how long dinosaurs were around!
By the way, even though some say it is wishful thinking, I recommend synthetic oil and grease after break-in. 