To be honest, neither of these two cases ticks my boxes but if I would want a case with a big side panel door, I would at least want the door to open the right way, i.e. towards the wall (although guess it all depends on how you locate your PC but in most pictures from users here, the back is towards the wall). With the Cosmo the door opens towards yourself which I personally find is just wrong, need about twice as much space at the side of the PC to be able to work comfortably with it unless unplugging it all and moving the PC each time and then having a full size panel door is a mot point.
As an enthusiast wouldn't you want to show of your PC bit more, especially if you paying £1500+ for it all, I know I would (and for the first time I will once my
Corsair 750D case arrives, hopefully today. lol )
Regarding the specs, both of them looks great so which ever one you pick there you will have one hell of a good PC for years to come!
But as been said already, case is a personal choice really, we just giving you our opinions, in the end it is you that will be looking at it for years to come.