Idk how much empty space for your support hand is ideal.
It’ll be subjective, I like to use the large one on my 19 but that’s from experimenting with all the grips at the range to find what I was most comfortable with.
Try some range time with both and see what is more comfortable to you while shooting.
It’s important to try it while shooting because that’s when it matters.
Pinky also plays a pretty big roll in how you yoink the gun to counter the recoil.
Down and to the right? Maybe grip a bit less with your pinky. Up and left? Maybe a bit more.
I’m not an expert, but I’d say as long as your primary hand is comfortable go with that, although support hand is the most important for shooting accurately. The pic you posted shows what looks like plenty of real estate for the support hand.
