E46Ms are great. I think they're more fragile overall so they can be a love/hate affair, but they're a hoot in their own right when sorted out.
I miss mine often, but that doesn't take anything away from the E90, just different cars that beat each other out in different ways. I find the E46 more engaging, old school feeling, which can be fun at any speed. The E90 is more capable and more livable, but only exciting when you're on it (which can be a good thing if it's a dual duty car). I wouldn't mind owning another E46 alongside the E90 someday. Mine was a Dinan S3 with RACs, Brembos, TC Klines, 6MT with SSK and UCP, CSL goodies, etc. I only moved on because I needed 4 doors. Here it is beating up
Jive's E92 ZCP in the hills a long time ago.