The different models have different grips, so if one doesn't work out for you - don't assume that none of them will. The Glock 19 finger groove spacing fits my hands perfectly - as does the G26 and G30. Those are my prefered models.
The full sized grips, G17/34/22/35 etc, have more space between the finger grooves.
The compact sized grips, G19/23 etc, have less space between the finger grooves.
The subcompact sized grips, G26/27 etc, have further slight differences. (if you take a very close look at the details of the frontstrap texturing)
That is just in the 9/40/357 Glocks. The .45/10mm Glocks also have different finger groove spacing. There is quite a range, so it is likely that at least one or two models would fit your hand nicely.
Not only that, but each size (full, compact, subcompact) have a different geometry to the backstrap that affects the overall feel. I prefer the backstrap angle of G26>G19>G17. Others prefer the opposite.
Another alternative would be to buy a 2nd generation Glock that doesn't have finger grooves - they are plentiful, cheap, and easy to find.
And of course you could always manually take the grooves off.
But to answer your question in two words, "My hands."