Which 308 semi - if any?
My question is why 308? I've got a DPMS LR-260 (260 Remington) with a Geissele trigger which gives better long range accuracy (mostly limited by wind deflection and vertical stringing) than any 308 semi or bolt I've shot and with less recoil. That's not to say the 260 is "better" for all uses.
The FNAR may be a great rifle. I haven't met one. The reviews are pretty good but those are rather subjective.
It would be nice to see some side by side comparisons of accuracy, reliability, and ergonomics under various conditions and ranges.
There are a lot of good 308 semi-autos available:
M1A
FAL
AR-10
LR-308
FNAR
SR-25
PSG-1
and several others.
It may just boil down to which you like or can afford.