Just who are these "professional level" shooters? Members of the firearms industry? Competition shooters? SWAT members? Active duty DEVGRU team guys? Of friggin' course there's gonna be decreases in performance with a smaller P365 as compared to a Glock 19 and similar size guns. No one in their right mind would suggest that micro-compacts can even equal the performance of full-size duty pistols (I consider the 19 a full-size gun, but some, I realize, do not). That said, I myself feel adequately armed if packing only a P365, as I'm not gonna be shooting for scores on paper targets or the fastest times against another competitor or type of handgun. I have actually trained with a micro-compact and am well aware of its capabilities and limitations.
Old Dog,
I am a full time LEO for 30 years, but have never competed. I have been shooting handguns for almost 50 years, so that should give you an idea of what my skill level and background are..
I carry a GLOCK 19 on duty, but a SIG 365 off duty.
There is no question in my mind that the SIG is the LESS CAPABLE weapon. It is harder for me to shoot with longer recovery times between shots.. With 11 rounds on board, I am not worried about the magazine capacity, but the shorter barrel means less burning time for the powder, so I expect lower velocity. I overcome that by using a top of the line defense load, FEDERAL HST 124 grain jhp.
Previously, I carried a GLOCK 42 in 380ACP and before that a WALTHER PPK in .32ACP. Prior to those, I carried a S&W J frame or CHARTER ARMS Undercover for almost 20 years, when off duty and not carrying my duty gun. The SIG is a harder gun to shoot, but is a major power upgrade from the GLOCK 42.
It is possible that someone can develop a "SHORT BARREL" load for the SIG and my other short barreled 9, a SPRINGFIELD ARMORY XD9, but what would it mean to me as a shooter. Greater recoil, muzzle blast and flash?
I have found that I can shoot the XD9 as well as the issue GLOCK 19 and it is more concealable, but not nearly as concealable as the SIG 365..
The short barrel of the SIG combined with the light weight and small grip area make the SIG a harder to control weapon than the GLOCK 19, even though it is not that much lighter.
When I shoot the SIG, I can easily tell the difference between the FEDERAL 115 grain fmj practice ammo and the SIG 124 grain jhp or FEDERAL 124 grain jhp HST load I carry for personal defense.
I suspect the American made ball ammo is loaded to lower velocity than the jhp ammo. Not surprising.
Recoil and the effect it has on my ability to control and shoot the SIG 365 is a major consideration. I am looking into alternative ammo selections.
On using multiple platforms, I would say that depends on the person.
In the last several weeks, I have shot the qualification drill my agency used before the present one, shooting a S&W model 15 .38 Special revolver, BERETTA 92D Brigadier in 9m.m. and BERETTA 96D VERTEC in .40 S&W and a .45 ACP STOEGER 8045 Cougar ( a BERETTA 8045 clone). I also shot a BERETTA .25ACP that was my wife's old gun, though I only shot a short range ( 10 yard ) course. Also, along with being an LEO, I am also a gun collector and informal shooter. Still, I usually shoot the same qualification or a variation of it depending on the gun and what I want to accomplish with it. It allows me to compare different guns, ammo and calibers.
With the exception of the .25ACP, I would feel well armed and full protected by any of these guns, even the .38 Special, although that would be my last choice. I think the real difference comes down to the individual person and their mindset.
I also work with a petite female agent who had too much trouble trying to conceal her midsize SIG pistol and requested that she be allowed to carry a SIG 365. She was allowed with the proviso, that she still had to shoot the standard qualification course and get a passing score. It is actually easier for her to shoot the SIG 365 that it is for me as her hand fits the gun better than mine.
Another officer I work with went with the .365 because like me, he can easily conceal it under casual clothes, although he carries inside the waistband.
Jim