I have both
Arched and flat, but I prefer the feel of the flat MSH. However, I also prefer the short trigger (all three of my 1911s sport short triggers). There should be more options, like which combination do you prefer. Arched/short, arched/long, flat/short, flat/long, wedge/short, wedge/long, well you get the idea. I'm a short/flat guy, the only arched MSH is for the historical "look" on my WWII GI, though it is a checkered Smith & Alexander with lanyard loop.
Just my 2¢
Robert