I have a G26 Gen 4 9mm, a Sig MK25 9mm, Sig M11-A1 9mm, Sig 226 9mm Elite Stainless, and a G33 Gen 4 357sig. I have a G27 barrel that allows my G33 to shoot .40 and 357sig X-Change Kits for the MK25 and M11-A1 along with .40 barrels for both the MK25 and M11-A1 x-change kits. So I have 9mm, .40, and 357sig pretty well covered and I have over 4000+ Speer Gold Dot ammo for HD/SD, enough to last me about 4 years.
Want to know what I EDC? G33 G4 or M11-A1 with 357sig x-change kit.
What to know why? Google "Speer-Gold-Dot-Ammunition-Comparison"
9mm+P 124 Gr GDHP = 1235 fps velocity, 420 ft lbs energy
40S&W 155 Gr GDHP = 1162 fps velocity, 465 ft lbs energy
357 Sig 125 Gr GDHP = 1379 fps velocity, 528 ft lbs energy
With the 357sig it seems to me like I shoot more accurately and my follow up shots are as quick or quicker and there is no denying that its going to hit harder and faster.
What's the big deal you ask? Nothing if you ask me. Shoot what ever you choose.
What advantage does the .357 SIG really offer you ask. It hits harder and gets there faster.