Both cars have there good & bad points.
tbh the chap with ZS 180 really needs to get in a ZR & test drive them back to back would be the only way to decide!
I made the switch myself from a mk2 ZS110 to a mk2 ZR105 back in july & have to say if anything i actually prefer the ZR, the seating position is higher up & i find it more comfortable, overall it suits my needs better!
Fuel wise it does use slightly less than my old ZS but i would expect this as it is a lighter car!