I've used both steppers and (especially) BLDC's (BPM) extensively. Maybe if you run a hybrid stepper with feedback [link|http://www.d3engineering.com/kruse.phtml?topic=imaging"|(e.g. Kruze control)] it's OK.
But the torque curves are sucky; stepper torque drops dramatically at higher speeds. They don't have the high peak torque of BLDC's, either. They don't handle high inertial loads well, and can stall. I doubt they're as smooth as the alternatives; definitely not very smooth if you don't microstep, and I've seen microstepping still be a lot rougher than I'd like.
I haven't used AC Induction or SR motors, but the article's analysis seems reasonable to me (and we try to avoid brush motors).