So between these two lenses, which lens will you get? Let me know and tell me the reason :)

A test against 300 pro would be interesting! Panasonic 200 + 1,4 vs  Olympus 300

Another amazing review! Thank you Richard.

another great video! Love your technical comparison

Well thought out  comparison. Thanks.
I own  the G9 and  PL100-400  and  find  the combination to be a wildlife  photographer's  dream.
But I've  been using  MFT for  a long time and  have more than a few other lenses and  cameras too.
A prime lens is always,  always going to be  sharper than a zoom.  A  zoom lens has to compromise. The PL100-400 is a X4 zoom, optimum is X3.  The wide  end  of  an extra-long zoom is intended for finding the  subject, not intended for taking photos; it is going to be soft there.  The  long end, it is usually best to haul it back slightly.  With the G9 and  the PL100-400 the AF is  almost instantaneous, it rarely gets it wrong. If  it is hunting, the  focus mode  is set wrong;   it probably  doesn't know  where you want it to focus and is  spoilt  for choice.
A  teleconverter expands  the  central area  of  a  lens. That may  improve corner  sharpness, but  you lose some contrast and DoF. Much depends  on the glass in it. There is  usually  some  compromise  with a  teleconverter. It will  never be  as good  as the bare lens,  on  a zoom lens  they will show up more faults.
I do not have  the  200 prime, I do have the 45-200 Mark 1 and  Mark 2.   The Mark 2 offers  Dual 2. They are a lot smaller than the  PL100-400.  The Mark 1 gets  mounted  on the E-M5ii,  it  cannot  tell the  difference.  The PZ45-175  is a hell  of a  lot smaller,  smaller than a cola  can and  nearly as  good  as the 45-200, it is tiny. With the PL-100-400 the  100-300 becomes  obsolete.
If  you have  the PL100-400 you do not want to lug  around another big lens.
It's often down to practicality. How much junk do you want to carry? Do you swap lenses out with wildlife or grab the other camera? Less is more.

Really great comparison! Not that I can afford either of these lenses yet, but the 200mm is a thing of beauty. Top of the want list for the sharpness and extra stop of light gathering

Thanks for the video!

Richard Wong. Great video, it has been of real value to me. I ordered an "excellent condition" secondhand 200mm f2.8 lens for £1149 this morning and it arrives tomorrow.

Thanks for the comparison.  Nicely done.  Having to insert and take out TC's is to much faffing around when shooting wildlife.  As the quality of the Leica 100 - 400 is still very good, the versatility and price of this lens makes it a clear winner for me.

Good review.  I find many get too caught up in pixel peeping rather than what really matters - which is getting the photo in the first place.

I've never missed a photo because my lens lacked sharpness.  But I've managed to get lot of great photos because I had 800mm 35mm equiv focal length when 300-400mm @35mm equiv simply wasn't enough.

I’m interested in the 200 prime as it’s better for sports.  Actually both are useful - depends on the use case

Thank you Richard for your video! Hmmmm. I have the 100-400 Leica and have gotten nothing but excellent sharpness with it, especially with G9/G9 II with Leica Dual IS, even at 400. I heard the 200 is crazy sharp, and I imagine sharper than the 100-400 from what I hear,  but I need that extra reach of the 100-400 for wildlife, particularly birding. I imagine you'll do more than just fine with either.

Thanks for doing this test!  One point of feedback, please do not use continuous autofocus, just set focus once and leave it, there is constant focus hunting in the video.

Great review/comparison
That 200 prime costs a fortune. It would want to be pretty damn brilliant for that price (which it is).

Great videos Richard, thanks for making it.
Will be interested to share speed of AF of the Leica 200mm on Olympus E-M1 Mark II body
and also comparison with Olympus mZuiko 300mm f/4.0 PRO with all combinations of teleconverters.

Great comparison.
Is is possible to use a 2x teleconverter on the 100-400mm? for exemple, to shoot the moon?

More Leicas, YES! Is that a Zeiss Ikon ZM behind you??

That is impressive sharpness wide open on the f2.8 200mm.  I use an adapted Canon 400mm f5.6L on the Lumix to get 800mm equivalent telephoto that is tack sharp for about $1200 with adapter. The AF is also quite good with the Kippon adapter. The reach is however just too much sometimes and need to step back or pull out my 100-300 Panasonic.  That 200mm with both teleconverters is a dream for Panasonic users and it clearly sweeps the floor with the 100-400 which is already expenisve for teh sharpness at $1798 ouch.  However the 200mm wich includes the 1.4x in the box plus the 2x for $3595 combined is exactly 2x the price. Which is no mistake by Panasonic.  If I had to choose I would buy the 200mm with the 1.4x tele and wait for the 2x to be available at a discounted price in the used market or when it is easier to afford.  For sports photographers the GH5 or G9 with the 200mm and both teleconverters is a lightweight professional dream house.

Thanks for the comparison. Already have 100-400 for more than a year now. A bit impressed by 200mm one.  But I’m not buying as it is too expensive.

Thanks for making these comparisons. I have had the 400mm for over a year. Use it for bird photography when I don't want to carry my heavier Nikon gear. But my one isn't as sharp as it should be when one considers how expensive it is. It's not nearly as sharp or consistent in focussing as my Nikon 200-500mm F5.6 (that covers similar range). It also struggles more in backlit situations and its VR isn't as quick to stabilise. Based on your video if I had to start over I would NOT get the 400mm lens. Maybe I might get the newer F2.8... but I would want to test it carefully first!