Allen head bolts (SHCS's) are better because:
They can be precisely torqued with a torque wrench.
When the fasteners do not need precise torquing a simple piece of black pipe becomes a universal breaker bar; Although I have a piece of drilled 5/8 dia. 1020 steel knurled on one end to provide a grip.
They can be accessed at an angle with a ball end driver with little chance of damage.
They can be had in an assortment of metals and finishes thru outlets such as McMaster-Carr. 18-8 Stainless Steel is my favorite.
SHCS's never required an impact wrench to remove, in my 25 years of experience anyway.
Allen wrenches store in a neat little container that provides an visual inventory when cleaning up, and when you grab the wrong one the required on is right next to it.
Besides I think there is just something wrong about using a fastener called a "cheese head"....
