Assuming those figures are accurate, the Cayman is a second quicker to 100. That's a lifetime, and given that it's a better handling car too it's going to be substantially quicker on road, track or strip.
Who cares anyway? It cost £20K more so you'd expect it to be better, and if you wanted a quicker car then go buy an old Impreza for £5K, spend £5K on go faster bits and you'll be quicker than 99% of the cars out there. The Zed is about the experience, the overall drive, not the pace.