In lead and denser metals (especially when considering shot such as steel), I believe pellet count is more important that velocity...
Especially with lead, it is easier to pattern slower loads than faster. 1300 FPS is fast for a lead load, and it is tough to keep such a fast load together. 1300 FPS would be considered low for the harder non-toxic loads (especially considering waterfowl loads), and the harder materials will pattern better at faster speeds than will lead...
With a 200 FPS difference there will be some difference at 40 to 50 yards as far as the energy maintained... The faster loads will have better energy and penetration capabilities... The slower load with a larger payload should have considerably more pellets in the center of the pattern at those long ranges though...
At 40 yards, the slower larger payload would most likely prove more effective, but I honestly don't know what the energy and penetration levels of such a slow load would be at 50 yards?