All ball valves are not the same. I saw some 3/4" that were about 1/2" on the inside. maybe thats why it was cheaper. You need to look and compare.
I would think a ball valve would allow you to "fine tune" the air flow better.
If I had the extra cash at the time of purchase, I think I would buy 1" valves for the extra flow.
22.5 WSM, 120 Gallon Offset, Weber Performer, IQ-110, ET-732