The iPhone 15 has the A16 Bionic chip. The 14 Plus might be less likely to force screen dimming when running hot since it is larger and can displace more heat. Six of one, half a dozen of the other for gaming.
I would probably go with the 14 Plus just for the larger screen size.
I had the very first Motorola Droid and was an Android user from then until the iPhone XS. Now I’m on my 3rd iPhone, I have an Apple Watch, two iPads, AirPods and AirPods Max, and am planning to buy a Mac. I got a taste and now I’m addicted!