The change to the arched mainspring housing (MSH), as I am sure you know, came about to improve the grip of the shooter. The design was to "fill the shooter's hand" and the serrations or checkering on the back of the arched MSH were to improve the grip as well.
That being said, I have 1911's with both styles of MHS(s) and notice no difference of point of impact or accuracy. The 1911A1 style does "fill the hand better" but, the straight MSH(s) that come on most new style 1911's are, for the most part, checkered and provide, IMO, a very comfortable grip.
The only real difference may be how your hand feels after an extended shooting session. The 1911A1 style MHS may have a slight advantage but, this again is only my opinion.