you need to think what you mean by comfortable
for some people it is air suspension...
for others a car with a big lazy engine
for others it is the suspension setup
for others it might be the size of the car (big absorbing bumps more)
these things are quite personal, and for me there is no car which suits the ways I want to drive at different times etc. - so I have a range of cars... the z3 you saw me in is a lot of fun on a nice sunny day on a country road - it is not comfortable bashing up a motorway for 5 hours which I do every couple of months to friends - generally it is not a comfortable car - the best I had for that was probably my range rovers - and I may get another soon... the skoda octavia is also comfortable in most circumstances, but while it handles well, it doesn't shrink around you in the same way as the z3 - different cars for different purposes...
Alasdair