[Klaus]

Unfortunately while the 12-60 F2.8-4 may just be a little smaller on the outside (98.5mm x 79.5mm), it's actually a little heavier at 575 g.... so forget about that aspect. Plus usually the brightness advantage disappears quickly and would only be fully available at the less useful wide angle side which for all intents and purposes makes it a f4 lens as well.

 

It will come down to optics for me because I don't see much else being different (incl. price)

 

This is the size of the Oly 12-60mm f/2.8-4 ? Did you take this one as a guidance ?