E90im- I understand exactly what you're going through. When I first got the E90 I wasnt really impressed with it. But day after day I love it more and more. IT's a great sedan IMHO. As for trading it in, I would think hard about it. Go to your dealer and sit in an E90 with aluminum trim and see if you like it first. If so, consider ordering an aftermarket al trim for it. If you test drove the Mazda and like it far better than the E90, then by all means buy it. You have to get what you want and be happy with it. IMO the Mazda looks pretty nice on the outside. I have never sat in one before so I dont know how the interior is. Think about getting the AL trim first. If it still doesnt make much of a difference, then go with the Mazda. BUT I HAVE TO TELL YOU: THINK VERY HARD ON IT!!! The last thing you want is to trade in the E90 and later beat yourself up about it. You also have to take your insurance into consideration.
Insurance companies think the E90 is a pretty safe car so the rate is definitely lower than the Mazda's. Also think of the free maintenance and how much it would cost you over the next few years. There are tons of features on the E90 that the mazda doesnt have. I got a flat tire on the freeway just 2 days ago and the thought of changing a tire on the shoulder scares the heck out of me. Cars were zooming by like crazy. If one of those cars happened to pick up a rock and send it towards me...You never know if some crazy bastard will just try and hit you while you're changing the tire.
The mazda is not a bad handling car and it also comes with limited slip diff. so its pretty decent in the corners. But again, think long and hard about EVERYTHING you will gain and everything you will be missing.G'luck