On this quiet, cold and rainy Sunday afternoon, I had a little time to kill. So I set out to capture test results from European publications (mostly German) for acceleration to compare the different M4 variants. To remove the effect of the added grip at launch provided by PSC2 when the cars are so fitted, I only set out to capture the 100 to 200km/h acceleration. I compiled 21 different tests and then averaged the results for each M4 variant (DCT only). While this is not the most scientific approach, it does provide a decent perspective. Here are the results:
100km/h - 200km/h acceleration
9.52 M4 Base (6 samples)
.... ∆ 0.20
9.32 M4 CP (9 samples)
.... ∆ 0.67
8.65 M4 CS (4 samples)
.... ∆ 0.20
8.45 M4 GTS (2 samples)
First, I think this dispels the rumours that the CP is not any quicker than the base model, having a ~0.2 second advantage from 100 to 200km/h. Second, it also shows how the CS pulls quite strongly in the top end, being ~0.7 seconds faster than the CP and only ~0.2 seconds short of the mighty water injected GTS. Which is in line with the conclusion reached in the OP when looking at the power charts
.