The conclusion of course is the most interesting part – the author ends with preferring the cheaper lens (the 1.2 lens is 3.5x the price) as the advantages of the Pro lens are not big enough (and there are downsides, too, e.g. the weight … oh, did I mention the price :-)?).
I hope we will see some more 1:1 comparisons in the future; Olympus is providing 3 cousins soon, the 16mm, 25mm and 45mm with 1:1.8 in their premium line, and the same with 1:1.2 in the Pro line.
In Panasonic’s lens line-up we find the Lumix 42.5mm 1:1.7 and the Leica Nocticron 42.5mm 1:1.2, the Lumix 25mm 1:1.7 (which is really a budget lens) and the fairly old Summilux 25mm 1:1.4. And then there are the duplicated 12-60mm zooms where it is already clear that the Lumix 12-60mm is a real bargain.
So what is your take on this? Personally I think that for the majority of shots you will be able to do without the Pro/Leica lenses. On top of that the cheaper cousins are significantly smaller and may suit smaller bodies better. That said – one of my current favourite lenses is the m.Zuiko 75mm – oh wait, that it not Pro-, only Premium-Line …