For sure. For me, flat side panels make it easier to get a consistent grip in the holster and help me keep the recoil arc consistent. I am measurably less consistent with the rounded profile grip modules (greater proportion of fumbled draws and slower splits while I wait for the sites). YMMV.
All that is speculation based on pictures. I don't have one in hand to try. The Wilson unit might be better on every measurable way, for me, and I plan to spend some money to find out. Even then, you may have a different experience.
I don't own a 320. I shot a full size model upon their release. It didn't fit, and the recoil impulse felt like a wet noodle. Upon handling a Carry model, I liked the shorter slide, but I held off buying one as they were still new. Then the drop thing came about. I thought the X frames would be the ticket, but I found the large and mediums to be too wide and the small to be too small.
I ordered one of the Wilson modules just to see how they feel figuring I could sell it if I didn't like it.
I like it. I like an out of the box grip option that doesn't require doubling the cost of the gun to get.
I'll probably try it on a demo gun or borrow a 320 and put some work in with it prior to actually buying a 320 however. If it doesn't give me an improvement over a G19, there is no point in going down that road.
I had an ER nurse in a class. I noticed she kept taking all head shots. Her response when asked why, "'I've seen too many people who have been shot in the chest putting up a fight in the ER." Point taken.
I recently transitioned from mostly shooting a CZ P-09 in USPSA Production (flat grip sides) to a P-10F in Carry Optics (slightly rounded grip sides).
At first the P-10 felt really strange and I had the same issues as you (poor recoil control, inconsistent grip on the draw). It took me about 1500 rounds to re-set my hands and brain. Now I can shoot both about equally well.
I ended up swinging by a Sig LE dealer on the way home. I handled a regular carry model. The only X frame they had was an X-Carry.
I know it's all subjective, but I "like" the feel and contour of the WC module the best. The standard module just feels like a freshly unwrapped bar of soap to me. The medium X frame is a bit wide for my taste.
I also thought I would like the flat trigger better. I didn't.
I had an ER nurse in a class. I noticed she kept taking all head shots. Her response when asked why, "'I've seen too many people who have been shot in the chest putting up a fight in the ER." Point taken.
Just to clarify when they say "any X-Series" Im assuming they mean any 17 round mag that doesn't have the tabs on each side that go into the cutout on the grip module and say Sig Sauer on the pad of say a standard compact model? Sorry there are so many variables with Sig