Everyone's hands are different: long fingers, short fingers, thin finger, fat fingers, in between fingers, long thumbs, short thumbs, big beefy palms, slim palms... you get the drift. The physiological makeup of your hands, wrist, forearms, etc., and your physical strength are the prime considerations in what kind of grip is
"right" for
you
The "thumbs forward" grip is a fairly recent development in the semi-auto pistol world, mostly brought about by competitive shooters within the varied "games", of which there is the great consideration for speed, down to the thousandths-of-a-second. In many of these competitions, the loads are powered down from full-house defensive rounds that one might pack in a daily carry weapon. There is considerably less recoil thus allowing faster recovery times and faster coarse times. Most semi-auto competitors swear by the thumbs forward technique as being superior to "locking" your thumbs downward, as in two-handed revolver shooting, which is (
still the proper grip for wheel guns.
That being said, thumbs forward is not necessarily the
best practice for truly defensive purposes. do whatever feels best and works best for
you.
As for myself, I have large hands with thick, medium-length fingers, and a have lot of body strength. I shoot both semis and revolvers the same way, with thumbs locked while two-handing. I
have tried thumbs forward; it feels alien, and just doesn't work for me. Those thumbs hangin' out in the breeze don't feel right, and I ain't too darned worried about a few thous' of a second recovery time in a defensive situation. Being quickest out of leather, having a strong, comfortable grip and getting sights on target pronto are my priorities.
But, hey, to each his own.