[thstone]

Why choose? Keep them both. I still own both cars.

I have a 2003 Miata and 1999 Boxster and have driven them both on the street and on the track. Here are my thoughts:

Miata:
Pros:
Super fun to drive. Effortless. Light clutch and silky smooth short-throw gearbox.
Easy to feel like a pro and get the most out of the car
Well balanced and precise handling
Very cheap to maintain and repair
Suspension/engine upgrades very cheap
Very reliable

Cons:
Low on power
Stock suspension has lots of body roll
Small interior
Flexy chassis/body
Definitely not a $50,000 car
People say its a chick car

Boxster:
Pros:
Flat-6 engine nirvana
Even more fun to drive if you're willing to make a bit of an effort (clutch is heavy, gearbox a bit clunky)
Much more power (and even more still in S model)
Perfectly balanced handling but takes more driving skill to get the most out of the car
Roomy interior
Nicer materials/build quality

Cons:
Expensive to repair and upgrade
Not as reliable
Engine can't be upgraded for more power (buy the S if you want the power because you can't upgrade the base engine)
IMS worries lurking in the back of your mind
People say its a chick car

The Boxster is a better car in terms of design, materials, and performance. The Miata is a better car in terms of ease of use, reliability, and affordability.

If I had to choose between the Miata and the Boxster, it would depend on what I used the car for. If I just wanted an easy to own and fun to drive sports car, then I'd keep the Miata. If performance was a priority and I wanted a car that turns more heads (and could afford keeping it), I'd keep the Boxster. I like the Boxster better by far. My wife chooses the Miata every time because she says that the Boxster just takes more effort than it is worth to her (she never drives fast).