Optics Ready Handgun - mainly for Steel Challenge and Fun

I'm interested in getting an optics ready handgun for shooting Steel Challenge and for general fun in the sun.

I see a lot of options out there and I'd like to know your thoughts and what you like.

Also - does the benefit of the long sight radius of a 5" gun become moot when you're shooting with a red dot? Or is there still an advantage (besides when the red dot stops working)?

I'm already a Walther guy, so there is the PPQ in both 4" and 5" models. I have a PPQ M2 Navy so it might just be a new slide - I don't know if they will be compatible and if they will sell them. If possible that would be a preference too because I have plenty of mags and a holster that would work already.
I also just don't like Glocks, nor do I shoot them well, so they are out.
Finally, I am sticking with 9mm.

Other options I've already seen (all available for around $650):
Canik TP9SFX Vortex package.
SIG P320 w/Romeo 1 package.
S&W M&P 9

What else should I consider?

CZP09, check out Cajun Gunworks version.