Few shoots taken with 5dIII+135/2 @f/2 and 1dIII+100/2, wide open as well.
Combo 5+135 works much better, I think it is faster, way better AF if shooting towards light. 135 does not require any MA, while 100/2 is -9 on may 1dIII and -14 on 5dIII. Both had hoods, set up in AV mode, same ISO, same setting in cameras. Used central AF point only. Developed in LR in default settings.
They both sharp, but 135 is sharper. Stopping down 100mm gives more sharpness and reduce CA, while 135 is razor sharp trough all apertures without/very little CA. 135mm on FF gives nicer bokeh and shallower DOF. Below pictures are links to full version.
Towards light
5dIII+135/2

1DIII+100/2 It was hard



Full version link
http://imageshack.com/a/img910/7199/LDOOaa.jpg
http://imageshack.com/a/img661/2189/wiflzG.jpg
https://imageshack.com/i/ipFAtN7Nj
https://imageshack.com/i/id0qXoZnj
http://imageshack.com/a/img661/2171/WvZAy3.jpg
http://imageshack.com/a/img912/1160/8nbdCM.jpg
https://imageshack.com/i/f0aqcd31j
https://imageshack.com/i/pc12M98Wj
http://imageshack.com/a/img538/5154/PM21Kw.jpg
http://imageshack.com/a/img661/2718/FCKZYY.jpg
https://imageshack.com/i/iddZUiaAj
https://imageshack.com/i/exD33Vodj
http://imageshack.com/a/img673/6836/yME1Tm.jpg
http://imageshack.com/a/img540/3749/OruFBm.jpg
https://imageshack.com/i/ipCh0t3vj
https://imageshack.com/i/exzdKrbhj
http://imageshack.com/a/img538/1215/DN1Xar.jpg
http://imageshack.com/a/img661/5449/9E7b4r.jpg
Nice set of comparison. Is it just me or does your 5D3 seem to be metering darker than your 1D3?

