I prefer 3/4 for house piping and 1 1/4 for a main line to the house and to
outside water valves (idea with large main is that you can water outside and
also get good flow inside).

I lived in house once which had all 3/4 pipes. It was great. Water flowed
fast everywhere. I have preferred this ever since.

Keep in mind that crud builds up on the inside of water pipes. So perhaps
with all the crud, the 3/4 pipe actually has 1/2 of remaining space whereas
the 1/2 pipe has maybe 1/4.