Actually, to tell you guys, i have tested 4 ABS-es.
1: XAS, newest hero version... Yeah, its flashy, Controls SUCK as hell.....
2: Mr.mo I liked it, but the hud is AWFUL, and its very hard to configure...
3: A evented system, quite nice, very customizable, but awful for a guy who cant sprite (same with all of above)
4: Babs, To be honest, when i tested this one, my first reaction was: Suckish controls, Ugly hud...etc, but when i looked closer at the config files, i began to like it more and more...
XAS
Pros: Demo is very flashy.
Cons: really NOT lagless... No smart enemies... F*ckd up controls... For non scripters and non spriters, very evil.....
BABS
Pros: Very customizable... Doesnt require spriting skills for weapons... Doesnt require heavy scripting skills...
Comes with a great config programm... Compatible with a LOT of other scripts... Lot of addons made for it!
Great forum with great people willing to help each other!!
EDIT# Doesnt need that heavy scripting work for the same result

Cons: Doesnt have a flashy demo... I want to have great sprites, but doesnt work for me ;P