After owning a total of 9 e46/e36 6 cylinders, I can say the following:
The e36 328i is in a league of its own in terms of Bang for the buck. It is definitely the more direct and engaging drive, although it depends on what you are looking for from the car. The e36 328i is still as thrilling as ever, even by todays performance standards. The e46 is ahead in terms of technology, looks (subjective), luxury feel and more importantly, safety. In terms off handling, you cant really say one is better than the other. the e46 has more user friendly handling, where the grip/handling reserves are closer to the surface while the e36 is more driver orientated, it can amaze you and make your heart skip a beat at the same time. In terms of reliabilty it depends on the previous maintenance history, although IMHO the e36 is more robust and durable than the e46, and will require quite abit less $$$ to keep in good shape.
You dont make mention if the e46 is a m52TU (2.0l) or m54 (2.2) variant. There is a massive difference between the two. The m52 (generally pre facelift) is abit weak and not really worth considering in this regard. The m54 2.2 is a whole different ball game. Unbelievable amount of grunt when you consider its the second smallest engine in the range. Both the e46 2.2 that I had have also been the lightest on fuel from all the 6 cylinders that I have owned (2 x e46 330i, 1x e46 325i, 4x e36 328i and 1 x e36 325i). My current 320i is returning 8.5l - 9l/100km on the mixed cycle.
It honestly depends on what you require from the car. Both have their pros and cons. But as I said, if this e46 is the 320i 2.0l pre facelift, then its e36 328i hands down.
The e46 320i 2.2l is extremely impressive for what it is, and is easily one of the most refined 6 cylinders ever. I prefer the engine character of the e46 320i m54 to the e46 325i to be honest.
I was in the same situation as you, and ultimately went with the e46 320i m54 for a few reasons...
