1911 Mainspring housing

I see that there is a preference in competitions and not only for the flat mainspring housing that the arched..any special reasons?

Flat, Arched....  Personally shot flat for 10 years.  Realized one day that there was a void in the heel of my hand when I gripped the gun. I now run the Wilson V..

Flat or arched is like grips. The use is what feels or functions best in the shooter's hand. We are not all exactly the same in build so altering the gun to obtain best results is why there are 2 main spring housing and why some alter the housing.  Same with length of trigger is adjusted to fit shooter's finger length and grip.