I've recently acquired another Mk 2 Capsule as I just love those omni's, they're so transparent and have such low noise, they're just extremely versatile. That said, just like any microphone, they each come with their own 'colour', or more so in this case, their own sound stage, with the cardioid pattern of the Mk 4 being much more punchy / mid supporting than the more open 'big' sound of the Mk 2 omnis. 

Now it's worth explaining here that I'm using 2 omni mk 2's outside the Telinga Dish also, so you're just comparing the bird sound here. 
I've applied my usual workflow, as the Mk 4 capsule does come with significant handling noise which I've become proficient at eliminating now but the Mk 2 capsule had absolutely zero handling noise, and that in itself can be a big game changer, so it's worth noting that. 

I will also be getting the Mk 21 soon, which is more of a wide cardioid and should in theory have slightly less handling noise than the mk 4 but will it sacrifice too much? 

It's all about the detail I find in this one, but those mk 2 capsules are so low noise, it also leaves room for boosting the highs in post to extract more detail in the highs. 

I'll let you decide which you prefer, but I can see the appeal in having both, as there are just some scenarios that each microphone capsule will bring something 'extra' to your subject, and that totally depends on the environment.

Wood Warbler - Schoeps CCM 2/Mk 2 - MixPre - 7039

Wood Warbler - Schoeps CCM4/Mk 4 - MixPre - 7037

Continuing with my comparisons between the Schoeps Mk 2 and the CCM 4 (mk 4). This was a challenging one as urban noises makes the comparison a little less 'like for like conditions' but generally if you listen to the bird quality over everything else you will hear a significant difference between the two. 

Gear: Sound Devices MixPre 6 ii / Schoeps CCM 4 inside Telinga dish + Stereo Mk 2's

New tracks tagged #Mk 4