ac30 is the more classic sounding one, preferably with the alnico blues speakers too. but the ac15 is still quite a good product, though i've had much time with it.
the AC30 is a classic amp, but it's very big and very heavy. its got a lot of bells and whistles. its also VERY loud. if you are not going to use it for big concerts/arenas, its quite a waste to have that much loudness on hand.
the AC15 is smaller, lighter, simpler, and pretty darned loud for home use. i think its just nice for small gigs unmiked, and will work very well miked up for large gigs.
as for classic-soundingness, i find that the AC30 and AC15 are both very classic sounding, neither is more classic sounding than the other. one is just a helluva lot louder than the other
as for me, i could tell that the AC15CC1X with the blue was sweeter sounding when i compared both, but the AC15CC sounded pretty darned good on its own as well.
i guess i just fell for that little extra sweetness (and also the legendary status) of the blue speaker and bought that one..