40 S&W is a loud, snappy round, and muzzle flash is all about what ammo you shoot, not wether it is a C model or not.
The C models are better for both self defense and recreational shooting.
In every self defense shooting scenario I have read about, one universal experience is that the shooter RODE their trigger hard. The adrenaline hit, and they dumped rounds as fast as they could pull the trigger. This is where C models really shine, as during fast firing the pistol stays flat, with very little muzzle rise. The importance of this cannot be over-stated.
Anyone that tries to tell you that there are visible flames shooting out of the ports and blinding them is full of s**t. Any pistol can have flash if cheap ammo is used, and good self defense ammo has next to no flash.
Shooting recreationally, the same attributes make accurate shooting easier. The pistol just stays flatter no matter what speed you are shooting at. Follow up shots are much faster as there is much less muzzle rise to deal with.
If you want to shoot competetively, and don't want to be all alone in your own class, then just get a 2nd non-ported barrel, and you're good to go.
There is so much internet b.s. about ported pistols that it's just stupid. There is NO logical reason to choose a non-ported pistol over a ported pistol. There is only MANY people that have no experience with ported pistols, and a severe lack of logic when it comes to this topic. It's basically just "I don't have a ported pistol, and have never shot one, so you shouldn't get one. Let me attempt to justify my position by spreading ignorant internet rumors, and telling you that you don't need a ported pistol because mine isn't ported and I don't think it's necessary."
Get the G23C, you'll love it.