Diesel made no sense for me: 5k miles p.a. and I just enjoy the sound of a 6-cyl (or more) petrol engine that revs properly. I couldn't have afforded the equivalent age 330d when I was buying my 330i anyway - higher-consumption of the petrol model benefitted me there.
I've previously owned a diesel "hot hatch" (Seat Ibiza Cupra TDI with 160ps/250lbft in a car weighing 1200kg) and enjoyed it, but it didn't ever have the wow factor of the Civic Type R or Clio 172 that preceded it. I quite enjoyed the way the Ibiza TDI delivered it's power, so much so that the other vehicle we own is my wife's Fabia vRS (130ps TDI) - I really enjoy driving the Fabia but couldn't have it as my only vehicle.
Ultimate 3-series for me (M3 excluded) would be manual 335i saloon. If M3 included then obviously M3, again saloon.
I'm 34 btw.
It's gone - no longer an e90 330i owner