Having owned (wifes car) and driven a Boxster for a number of years, I can give a simple point by point opinion of each.
Boxster:
Pros--
- Great fair weather car (can't beat a convertible with the sun on your face).. however the 370z has this covered now as well.
- Surprisingly comfortable on longer trips
- Trunk space is a bit better than expected and for those really large items, you can always drop the top and use the passenger side to get that coatrack home
- Superb handling in stock form.
- Nice features, quality feel.
Cons--
- Quick but runs outta steam compared to lesser priced cars (370z)
- Chick car styling. Let's face it, this is a chick car. (The Cayman isn't much better as it's called the "Cockster")
- Expensive upkeep.
- For the price you pay, Porsche's ALWAYS need to come equiped with STANDARD things such as Xenon lights, multi-disc CD players, etc. They do not.
- Did I mention it's a chick car? The only thing a guy could drive that looks more pathetic is a VW Beetle.
370z:
Pros--
- Interior styling and quality is on par or better than that of the Boxster (well it is with my touring package anyway)
- More powaa!!
- I've seen women driving them and it's sexy but it's not a "chicks car" like the Boxster.
- Lower maintenence costs.
- Lot's more pro's...
Cons--
- Small trunk space. It was better in the Boxster.
- Same blind spots as a Boxster with it's top up.
Porsche is a strong company but if I ever get a Porsche again (and I plan to), it will be a GT2 or GT3. Between the Boxster (or even the "Cockster") and a 370z... There's really NO comparison. 370z all the way.