I can’t answer your question, other than to say I found the 12-100 too large and I’m not a fan of variable aperture lenses or widest aperture being f/4, so I opted for the 12-40mm f/2.8.
(I do own the 8-18mm variable aperture lens, because I dislike the bulbous front of the Olympus 7-14mm more than I dislike variable aperture).
I had both of those lenses for a time. I found myself always choosing to take the Olympus lens due to the extra reach and in my opinion nicer rendering, so ended up giving away the PanaLeica lens.
Are you shooting an Olympus camera or a Panasonic camera? The 12-100mm f/4 offers 'Synch IS' on Olympus bodies, it won't function on Panasonic bodies.
I have the 12-100mm and the stabilization on my E-M1X and OM-1 Mkll is downright insane. It is a very sharp lens at all focal lengths and at all apertures. Its only down side is that it is a little large and heavy -- but it is a Pro grade lens.
If I could only keep one lens I own it would have to be this lens -- it is just too versatile.
I chose the Olympus 12-40 f/2.8 PRO over the Panasonic Leica 12-60 f/2.8-4 because it just felt more than usable to get 80mm FF equivalent on the long end and also keep that brighter f/2.8 aperture for times where it was really needed at night. I love it!
I have both (and many others, 12-40/2.8, 12-45/4...). The 12-100 is better optically, a dream lens when travelling but also slightly too big to be convenient for me.
So a year ago, I bought the 12-60/2.8-4 to get a compact lens with more reach than the 12-40 or 12-45. I can complement it with a 35-100/4-5.6 if needed.
And it proved to be a winner. Going up to 60mm makes all the difference compared to the 12-40.
I also shoot social events and theater. I never used the 12-100: too big, f/4 even a short focal length... I tried but it was not a good fit.
But the 12-60 does 80% of the job, meaning I use the extra Pana 50-200/2.8 I needed for portraits a lot less.
So I plan to sell the 12-100 but if it fits your needs, this is one the best lenses I have ever used.
I have both and kept both. The 12-60 has nice IQ and the highest mag is on the long end and is small for what it is. The 12-60 fits in my hiking pack well where the 12-100 does not. I miss the sync IS but that is not a killer for the12-60. We sometimes do these hiking Inn to Inn trips and I leave the other gear at a stop and retrieve it later. The macro on the 12-100 f4 natively isn't as good but I found a Sigma achromatic close up diopter that works well with it. If not hiking I use the 12-100 for the extra reach and sync IS but both have there place.