My hands are XL. On the standard XL frame my fingers wrap completely around the grip.
1) The ability to add a big backstrap (FDEZ3) to the Macro creates some grip space for my support hand.
2) The backstrap locks my hand in better, helping with recoil control
3) The slightly wider grip fills my hand better to provide more consistency in my grip.
4) Logistics: Holster compatibility when moving between XL-length and Macro grip modules (although I just tried an XL frame in a Macro Tenicor and it clicked in just fine so maybe I'm overthinking that.)
5) Logistics: Only need one TLR7-Sub
Shape and specifically size of the XL grip makes it feel like im holding a zippo lighter. I get much better recoil control from the Macro circumference and length. I found an XL frame and built it up to where it feels the same but would rather have a chopped Macro for the holster compatibility.