Seems to be the consensus as Purple says. MX-5 is often described as the best driving car in it's class/price range.
Haven't driven a Z3 myself, but I think the MX-5 is brilliant to drive (you just feel like laughing) - and better to look at IMO.
Oh and it's more reliable.
and cheaper.
and a bit less of a girly reputation - if it matters - wouldn't to me TBH.