Powder burning rates have absolutely nothing to do with recoil, science proved this years ago but reloaders seem to still ignore the results. So far as patterns go, each change in your load should be followed by a trip to the pattern board. Different speed loads hit the forcing and choke with different force, and these can make a difference in the patterns your gun will throw. Once you have a found a load choke combo that works for your gun at the distance you are shooting, stick with it.