Both are great weapons. I prefer the G3 over the FAL. The boltsystem of the G3 is great. Reduces the recoil and I have the feeling of a "cleaner" recoil. Also it's easier to upgrade the G3 because you can use MP5 parts (rails, stocks etc). Somehow I find the G3 more ergonomic, but maybe that's just me.
Never had problems with the zero of the G3. The sights are very stable, maybe just talk.
Both are great rifles, just depends on your preferance. I have a FAL variant which I'm content with, but I'd probably be just as happy with an HK.
I do think that parts and magazines tend to be a little more readily available for the FAL nowadays, since there are so many variants and rifles made on US-made receivers.
The Portuguese Army gets some thousands of FAL and G-3 and test them in Africa in the 60’s. In the end they say that both weapons were great, the FAL were more accurate but the G-3 were more reliable. In the end they choose the G-3.
I personally picked a Fal over the G3/HK91, though these were all semi auto variants. The Fal had the better ergonomics for my taste, I quite liked its sights, and perferred the balance of the rifle over the G3 so I went with that. Either one is a fine battle rifle.
I do wish someone would release the original prototype designs for the FAL back when they were working with .280 and the rifle was much smaller and chambered for a modern round of similar size. Would make an awesome rifle.
Both are good, I used the FAL during my time in the service, before we changed to the AUG. The Fal was very reliable and quite accurate. Today I own an L1A1 but I'm not very happy with it because the barrel is "kaputt" and I can't get my hands on a new one. I twice had the opportunity to shoot the G3 and I prefer it to the Fal. Alltough the only real issue I had with the Fal is its excessive length with can get you in tight spots when you are in confined spaces like mout or forests with dense undergrowth.
i've owned several of each in semi form, i foolishly got rid of them and now want to get back into the 1960's-1970's battle rifle club. the hk has a vastly superior trigger and sights. had more accessories. balance was off for me and i found it particularily nose heavy. i subjectively believe that the hk had less felt recoil and had better accuracy. oh and mags are about a buck a pop if you know where to look.
but i still like the fal. the balance was better for me. but the sights were almost as bad as ak sights. the trigger is the worst part of the fal because you can't (using factory parts) bring the trigger weight down.
also, imho dsa are way too pricey - $1,500 for a stg58! $1,800 for a us made parts sa58.