Well, when you say Koni specials, I assume you are talking about the usual off-the shelf models. You're going to have a hard time finding people who have tried both.
I will say that I've ridden in AGX equipped cars and a car equipped with Motivational coilovers (modified Koni inserts) and the Motivationals were far and away the best street set-up I've experienced for ride. I'm really impressed.
You also didn't mention springs or spring rates. I have AGX in my G20 and with (relatively low) 275/200 rates, I think the AGX are marginal. Then again, we have them on our B13 SE-R SCCA ITS race car and they are marginal there, but with much higher 450/400 rates. My opinion is the AGX are good for the money, but not my personal first choice. I got them for my G20 because I got a killer cheap deal on a barely used set. Otherwise, I'd have some sort of Konis in it.
I have Koni's and all my friends have AGX's. My car is far more comfortable then the AGX's. Plus if you do decide to go coilover the Koni's will accept the custom perch's for the coilover sleeves that are much nicer then the AGX's. Losing the external adjustment is a big loss though so it is a little bit of a toss up.