I took out a new M3 (E92) for a test drive today. I think you made the right choice.
Sure the beast is farken quick and does it with so much ease, way more so than my Sabine, but I was left impressed but uninspired.
At least the Z4 has loads of character. It may not be the fastest thing on the road, but it involves me and entertains me and enthuses me.
I can only imagine that the 330 and probably the 335 are similar, but without the much higher limits the M3 has. Fast, really fast. Boring.
Give me a car that makes me feel alive, inspired, living on the edge. Keep the 3 series for grandpa.