>>401948212-45 is a great walkaround lens. Good in a studio too with all that sharpness and you have control of light. I own it and use it all the time.
That said, there are multiple reasons why I prefer the 12-40 a good amount of the time:
MF Clutch is much better for video with it's hard stops. That extra step of light IS crucial in low light, and it was the difference of barely being able to shoot a concert at 6400 iso or it being a lost cause with blurry images at lower shutter speed or nasty noise at 8000-12800 iso. Pic related. It's still mushy and gross with Topaz cleaning up iso 6400, but it would be totally ruined with the f4.
Also, if you have a larger body like an E-M1 ii / iii the weight difference is not really a factor.
