Location: Chapel Hill, NC - UA Nobody (sigh)/0.918MM, HHonors Diamond
I've stayed in both of them and I'd say they are probably equidistant from your destination. Can't speak to whether the drive times would be the same, but do allow plenty of time. Traffic is pretty bad.
The Hilton is a nicer property IMO, although the HGI is in a nicer area. If you're just there for business, I'd pick the Hilton.