Best fit, feel, naturally in your hand
...
That, and point to aim plus, what you can or want to invest, as it should be a long time commitment.
Have the gun clerk demonstrate the ease or difficulty of disassemble and reassemble of each gun.. because you're gonna have to do it, yourself.
Personally, I can speak highly of the EASE of this procedure with any of my Sigs. All have shot, 100% no problems, and "accurate out of the box."
I can also speak highly of my P229 CT Carry 9mm, 2000 rounds, no jams, no failure to fire, just 100%.
Also, I'm sure the slightly longer, thinner, P226R 9mm is as sound.
But it should be what feels best, naturally, in your hand, and your investment dollars.
Good luck,
LS