I know you'll get a thousand opinions here, so here's mine...
I've long worn 800g rubber boots, but in recent years have actually gone back to leather boots, AND went down to 400g. Reason being I don't want the bulk and weight of really heavy insulated boots (1200g/1600g/2000g). And honestly 90% of the days our whole season the 400g are perfect. When it gets really cold (say 30's and less) I'll just use Toasty Toes. I wear 400g Danner High Ground boots and have yet to have even a hint of cold toes, even with temps in single digits a few times.
Danner is my top pick. I'm a very hot natured person, but my feet get cold normally. I don't mean just when I hunt either. I have to have a higher gram. The problem is with those rubber boots my feet sweat too bad. That's why I'm going back to lace up leather boots.