Both are good choices. Check your ancillary items to see what you might like to add on. Mags, and their prices, scope mounts, or bipods. They all help contribute to your use and comfort.
I have always felt from an ergonomic standpoint, the FAL is superior. Bit more of a finely crafted arm rather than a big stick. The G3 works, works reliably, but has always felt like a big clunky hunk of a weapon to me. Firing and recoil impulse don't seem significantly different to me, but operation of the G3 is just so much more manhandling than the beautiful and sleek FAL. In a head to head, I do think the delayed recoil system of the G3 has less to go wrong, but a properly build FAL should gives years of trouble free service as long as you do your part.
Suggestion. Look at the Commonwealth pattern rifle, L1A1. The Brits did many nice improvements to the type with superior fire control system upgrades and a sturdy mag upgrade. Small details, but it is in those details that take the FAL one step closure to perfection.
Or get an M1A. LOL