I have the PEK and started way back with the Desktop Evo wehn it came out.
I think it sounds way more organic and unique than the P12. But it comes at a price: you got to dig early 80ies digital artefacts in hybrid-synths like the Waldorf Wave or the PPG and of course the Prophet VS. It lacks the morphing abilities of the VS. (you can only fade 2 waveforms via the modulation matrix by crossfading them) But still it has a very old-schoolish vibe to it.
It can do bread-and butter analog sounds too if you turn down the distortion and other digital components in the signal path, but then you have to be careful with gain staging. It's very hard to come by the PEK with e.g. headphones. It can do thick analog patches, but that means keeping the OSC Levels down and make up for the gain loss with an external mixer or preamp.
The Combo/Multi Mode on the PEK isn't perfect, as you can't store individual patches from it , only the setup and configuration of up to four patches. But it's definitely more powerful than the 2-layer workflow of the P08 and P12. The Mopho 4X again is simply Monotimbral, so not a winner either in that category.
So in sum I'd say the PEK is a powerful beast, that sometimes is hard to control and to come by, but it can shine brightly and you'll never exhaust its possibilities even after years.
Just recently someone made a very nice soundset for the evolver line and the sound samples are the best you can find when it comes to pure evolver bliss:
http://www.boxedear.com/tqsevolver.php