The hosebib is considered 2.5 fixture units. 1/2" would be fine for it.
I have also run them with 3/4", but it was mainly to slow the water through the pipe. Less speed, less noise.
I notice that the last one I installed in my home, which was run with 1/2" PEX, is very quiet.
The previous ones that are run with copper 1/2" make more noise.
All three are washerless Legend frostfree hosebibs.