40-150 vs 80-200

I have a Pentax-M 200 f4 and it is also a nice sharp lens.  It isn't very heavy at 405g but it is pretty long at 13cm and it is the length more than the weight which makes holding it steady, even with the OM-D IBIS set at 200mm, a real challenge.  I often have to shoot at 1/320 to get a sharp shot.  And even with a fast shutter speed, the contrast is lower so finding the focus point isn't easy.  And using the telezoom while your hand shakes...  well, without a tripod and a lot of time to compose a shot and focus it is just hit or miss.

My best shots are in bright sunlight with a monopod or tripod.  On the other hand, I have a Pentax-M 100mm f2.8 which weighs 225g and is only 7cm long.  It has enough contrast to make focusing easy and I never have problems with hand holding or IBIS.

Net: on the OM-D, in my experience, the length of the lens matters more than the weight.