Keep in mind, the c6 corvette weighs about the SAME as the Boxster. The S model weighs almost 100 lbs MORE than the c6.
That being said, I think the difference between Porsches and high powered domestics is that Porsches are precision refined vehicles, whereas corvettes are raw, nasty and big.
The corvette has a much longer wheelbase than the Boxster, which is one of the reasons I didn't get one. I like a small car I guess.
But the corvette is no wimp in twisties either, like I said, it weighs just over 2800 lbs, just like the Boxster.
So I guess the answer is that these are different vehicles in different classes and you have to decide what you like
