At airsoft ranges and with the ''accuracy'' of airsoft guns, an irons setup for speed over grouping is far preferable I'd say. Airsoft guns in general are only capable of firing as accurately as the real thing (i.e. where your zero'd sights point is where the bullet goes, every time) within a small distance. A good quality AK can put 762x39 within about 3-4" at 100 yards, I'm not sure what the max distance would be for an AEG to attain that tight of a group as I'm just not interested in barrels/hop parts/internals, but I'd wager something very roughly around 20m (gun dependent obviously), followed with a max range of about 55-60m for a 350FPS gun that's been extremely thoroughly tuned by a very gifted tech.
That ties in to the proliferation of red dots within airsofting, how many people do you even see that don't run a dot sight? I mean when I think back it's a very rare sight for me personally. Get a few guys with 4x ACOGs/Specters and obviously there's the marksmen/snipers. Few older style guns (often AKs) just running irons, but more often just because they don't have any picatinny on top of the rifle. But outside of that, everyone I personally see with a gun that can easily mount a dot seems to have one and it does makes sense realy. In the real world if you're an awesome shot with a lot of training you can shoot someone at 700m with a dot, but it's a whole truck load easier with magnification, even a biff like me can hit a man at 500 yards with zero prior practice shooting at that range at all, long as I've got a SUSAT. However the concept of red dots was really tailored for close range encounters (10-200m ish, opinions and SOPs vary a lot) and the standard airsoft combat ranges of about 10-50m fit in that bracket very nicely indeed. You only have one point of reference which in the iron sight world would just be crazy, nobody does that, but we're so close in airsoft and the average carbines most people carry just don't shoot shoot anywhere near tight enough to worry about maximising sight radius and spending ages perfectly zeroing optics. Whereas being able to get a bead someone that's close very quickly is very useful indeed. A quick zero with a reasonable quality (or for AEGs even low quality) red dot works great I find.
Usual caveat that obviously all the above is just based on my own experiences, your mileage may and quite possibly will vary.