He E92 is not a better car in every way. In fact I think it's probably on the more away from the M3 recipe side of the scale. It's big heavy and not like an M3 at all. Don't get me wrong it's a good car just not a great car. The engine is sublime, but the size weight and even looks... Like I said had an e46 for 3 years e92 for 3 years and the Z4M for 3 years. No doubt the e92 is the quickest, but it does have the edgy sharp turn in the e86 and e46 does it's more like an American muscle car because it was designed for the American market. The e46 does everything well, and is like a go kart. The e86 is also a brilliant car but in standard guise the e46 handles better less understeer and less skitish but the e86 is no doubt the best looking and most special car. Depends what you want. The Z4M was always a very niche market most people when they came out didn't understand why you would spend the same money for a worse handling smaller 2 seater with a roof and bought the M3. Takes a very specific need or want for the Z4M coupe. Now 3-4 years ago they were bargain basement M cars few mods and they are sublime motors. Now they are becoming more a cult classic. I absolutely loved mine best looking car and there's not much that it can't keep up with in fact has the same time round Nuremberg as the lambo gallardo mk1. Impressive motor. The E46 slightly heavier and slightly slower but like a go kart so easy to stick the back end out so much fun and feels so involved to drive. The e92 is a little more disconnected in that respect but in a straight line will murder both. Problem is that high revving engine it's impossible to get up to the 6500-8000 because in second your already loosing your licence so hard to work on the road and gets murdered mid range by hot hatches. But when you put your foot down the power just never ends its pulls and pulls and pulls! Incredible engine. Wish they had used it in more than one car, seems like such an oversight. So it depends what you want the M3s are not sports cars they are fast saloons. The Z4M is a typical sports car two seats big engine big bonnet and you sit well back over the rear axel. The M3s make great dailies the e46 is slower but more fun in the twisties and the e92 great in a straight line. The E86 is the rarest, best looking and most special car imo but is more a weekend car although if your a single bloke or only have two people then it can be a great daily too. Sort the suspension and its the best bang for buck money can buy atm. Well it was, like I said the cars are now in worse condition and 3 years older than when I bought mine and looking at 2k more. Depressing how many poor examples are demanding high money.
