Length of Service and Availability in the USA
The AUG has been on the civilian market in the USA since the 1980's. The Tavor, well it has been on the US market since March of 2013. Will the Tavor's numbers dwarf that of the AUG? Eventually, it is possible, but for now the AUG has it beat there.
And the Rest
The biggest thing though, is the newness. Who knows what could happen in the future. If some sort of import ban or EO were to come down, you would be rather boned if you had an AUG or a Tavor. The difference is the AUG has a 30 year history in the US, with parts being available right now, and potentially in the future. As for the Tavor, who knows what would be available. If something were to happen in Israel where many of the parts come from, that would also hamper availability and production.