At first I had the same reaction some others have had... how can you compare a BMW Z4 to a Mazda Miata? But the more I thought about it the more I thought a comparison is a reasonable request.
I owned two Miatas and my current 2009 Z4. Here are my thoughts. My first Miata was a 1999 and had a fair amount of miles. But I only paid $4000.00 for it. I look back on that car and think, " I had just as much fun in that car than I'm having in a car that cost me ten times as much." I also like how I didn't have to worry about every stone chip or small scratch. Plus that car had character. It had that vintage, I've-been-around-the-block feel... like a beat-up Harley the movie star drives with some hot woman's arms wrapped around him as they drive down Route 66 in a black and white movie.
Don't get me wrong... I love my Z4. It's faster, handles so much better, ride is much nicer from a sporty perspective and from a luxury perspective. Everything from about the Z4 is nicer, more refined, classier. But it won't have that character until it gets 50,000 miles plus, has those age marks, and the seats all show wear from my fat ass.
So, in conclusion, is a sleek, sporty $45,000 BMW Z4 a better, more fun car than a used, somewhat dented, ripped-seats Mazda Miata? The rational part of me says, "NO." But the irrational part of me that walks out in the garage ten times a day just to look at his Z4 says he'd never think to own a Miata again.