From a German tester, who tests pretty much of all the BK stuff, i understood the XL was the same in torque and power than the 1950. Or do you mean that you personally would take a 1940 or the wanderer XL, because of it's overall preformance/temps?
I really didn't knew the 1950 came with a 5mm shaft. the BK site tells us it comes with a 4 and the other 19 series are available with a 4 as well.