Another sideline reporter here
though I've owned the 16-45.
I cannot speak optically but mechanically they are very different - and that alone is important. The 16-45's most bizarre feature (full length at 16mm, blocking flash output) is removed, WR is in place, and quiet DC motor too. From 16-45mm the new lens is f/3.5-4.5
(per Heie's review) so speed-wise it's nearly a draw. Whether these are worth 3x the price, that's each person's call. I loved the 16-45 except for its ending at 45, so that's definitely "fixed"