Imbels were always forged, whereas FN went to cast in the 1970's.
I would wager Steyr made the absolute best FAL's on the planet. DSA's are almost certainly equal in quality to FN's products, perhaps even better. Imbels were basic but probably equal to FN's, too, better perhaps because of the forged receivers. Who knows?
Some people like Type I or II receivers over the Type III's. However, the Type III receivers, while being heavier and less refined in appearance, are likely actually sturdier than the other types.
Ash