Leica M9 - 585g
Leica M240 - 680g
Leica M10 - 660g
Leica M11 black - 540g
Panasonic G9 - 688g
Panasonic S5 - 714g
Nikon Zf - 710g
The weight difference between the M9 and S5 doesn't bother me at all, I've carried the S5 with a small lens all day and not felt it in any way more than the M9. The Zf is a few grams lighter than the S5, and with a light lens, wouldn't feel any different. I did a shoot over the weekend with the S5 and as much as I love my M9, autofocus is just so handy for quickly capturing subjects. The Zf inherits the autofocus system of the Z8, which is supposed to be excellent.
I hate to say it, but the S5 would not have this rock solid AF in those conditions. Maybe the S5 II would, but I haven't seen any videos like this of the S5 II.
It currently has a street price of AUD $3500, which is no way near Leica money, even secondhand Leica money. Like always, I'll sit on the decision while the early adopter reports come in, but this is such a tempting camera.