Although once mature, they are very meaty and well filled out birds, they're also very slow growers so not the best choice for meat but still certainly do-able and edible!
The best time to process one is anywhere from 7 months on up. They don't finish maturing til well after a year old though.
The thing to know with Aseels is that they're a naturally very aggressive bird towards other chickens, both female and male. Males will fight each other at a very young age and must be separated. Males and females can get along as pairs/trios but females are indeed also known to start fights.
Beyond that, Aseels are an extremely intelligent and ancient breed who are very friendly and non-aggressive towards humans, probably among the most predictably non-violent and stable of breeds towards humans due to breeding for hundreds of years against such behavior. Hens make very good, protective mothers and both genders are excellent foragers and have good natural instinct.
I personally have no experience with them but I do know the related Shamo and Thailand Gamefowl, who are very similar just slightly less aggressive and larger than most Aseels.
My general opinion is that they're a wonderful breed, certainly worth having, but they're not a beginner's breed. One always starts somewhere with them though, so if you have some, best to do some research before breeding them, otherwise you just might have a crazy surprise once the youngins start maturing.