I have one of each. my .36 has a straight Long Hammock 36 inch barrel. my .40 is a Colerain a-weight swamped 42' with radius groove rifling. although the .40 is a precarve (whereas the .36 is my own warts-and-all), I would pick the .40 over the .36 if I had to pick one over the other.
the .40 caliber will hold velocity a bit better, is a tad less susceptible to wind, and (if you hunt) has a little bit more 'whompability.' (much has been made of hunting white tail deer with a .40; I think that this is not really such a good idea) the .36 is cheaper to feed, if this is a big item of concern... I haven't done the arithmetic, but I suspect it's pennies a shot ... if I'm that poor, I should probably be doing something more profitable with my time ...
just one guy's opinion ... free and doubtless well worth the price ...
either way, make good smoke! :grin: