Charles,
Get yourself onto the Titanic list - detailed discussion about the comparison there!
In a nutshell ... Box is much much crisper, probably because of the fact that 120k miles on shocks and bushes takes it's toll on the S2 (hence this thread ... ) Turn-in is magical, but high-speed stability is not as good (despite higher milage on S2).
Box is uninspiring in low ranges, but has a sharp increase in pep at around 5k rpm. And sounds delicious when it gets there. Generally though I think it is a slower car than the S2. (Not sure what the figures say.)
However the Box (56 plate, 2.7) feels slightly nanny-ish, getting very nanny-ish when you drive it hard. It has PSM, and if you try to do something you shouldn't, it tells you off and brings everything back into line. You REALLY need to try to get the back end out. If you give it too much beans on take-off, it cuts the power. If you don't give it enough beans, it ups the power. The traction control cuts in at various times and keeps you nice and safe. I REALLY don't like this. (It even won't let you open the doors unless it thinks things are safe.)
Of course, I could turn the PSM off, but it's a courtesy car so I don't want to chance it ... (moi? Coward? Damn right.)
An interesting observation is that the 944 and the Boxster are worthy of comparison. Despite my S2 being 20 years old (and based on a design that's much more than this.) That is seriously impressive.
Oli.