Is there any benefit to upsizing to 3/4" pipe off a 1/2" main supply?
Flow resistance, like electrical resistance, increases with conductor length. If you are going a long way (say, over 50 meters) you will get better flow by running a larger pipe. The volume is a non-issue - (static) pressure won't go down even if you install one of those giant green gas storage containers in the yard.

In no case will you get more flow than what the incoming pipe can provide, larger pipes just mean you will not lose part of this flow to resistance.

In a standard house you don't have enough piping (or demand) to make a difference.