Optics wise, I feel its better than 16-45.. but in term of Focus Speed.. slightly or maybe Marginal.. so since you dun have SDM, dun bother.. SDM only make Focus sounds Smoother..hopefully they will have new firmwares that makes its focus speed faster...:think:
The difference in focusing speed between the DA16-45 and DA*16-50 wide angle zoom is in my view not that significant. However focusing speed on the DA*50-135 telezoom is definitely fast. So I would conclude that SDM really shines on the tele end. Frankly I'm not too concerned with focus speed but on focus accuracy (i.e. no front or back focusing).