I own both a G3 clone on a Federal Arms Aluminum receiver. This is the one with the scope rail built in, and I also own a STG-58 clone built up on a Imbel Receiver.
The G3 clone worked right out of the box, and goes bang everytime. I have yet to attempt to produce any tight groups with it, but it will easily drill holes in a human sized target at 100 yards all day long. The recoil is very moderate. However it spits the hulls about 6 stands across the firing line. Magazines right now are cheap, intreordance has used mags for around 7 or 8 buck. I just bought a half dozen NIW RheinMettal G3 Steel mags for 15 bucks each.
The FAL Imbel clone however did not go bang out of the box. It required first and foremost a new non-2piece-o-junk, gas pistol. The orignal century two-piece piston, bent up after about half a mag. I had to replace it with a DSA piston to get the rifle to even begin to work. I then had to drill out the Gas port larger as the rifle would not consistantly cycle even on the highest gas setting. The recoil of the rifle is pretty fierce. A much more pronounced shock to the shoulder compared to the G3's delayed roller action with feels more like a slow push vs's the FAL's hard punch. I even welded a zero-climb brake on the muzzel , but the FAL still kicks like a Mule in comparison. Mags are cheaper but Decent ones still cost 10+ bucks which is on par with the G3 mags from intreordnance. I have yet to get any accuracy fell for the gun since all I have worried about is getting it to cycle properly.
The end result being that, I would not trust my life to either gun. If this is what you are looking for, buy an AK or a good AR. However the FAL definately has the "cool" factor going for it and feels more refined in your hands. Better ergonomics than the G3, especially the charging handle setup.
The G3, I beleive is more inherently accurate and out of the box more reliable, at least in my experience. However it doesn't look as cool and feels more clunky since it weighs about twice as much as the FAL.
Bottom line in my limited experience. The G3 will go bang every time out of the box. The FAL is better ergonomically and "cooler" looking but will probably require some modifications, a one piece gas piston at minimum, to work properly.
JBNTEX