2.7L vs. 2.5L?

[Perfectlap]

also look up the Consumer Reports evals on Boxsters through the years. Excellence magazine has a good market review for 986's noting the differences between years (even they all look the same from the outside).
I think the 2000-2002 reported the least amount of engine/drivetrain issues from
1997-2004.
As for power I've said it before, a car at this curb weight should have at least 240 HP. The car will be fine with less but it without question seems to "come alive" in the turns with the extra power. And of course for freeway merging and overtaking slower cars its very very handy. This car could easily handle another 100 HP with the steering and balance on hand.
As for resale there is no way to predict what the market will do but its a safe bet you'll get more money for the S. With the internet producing smarter and smarter buyers (like you) doing their research they'll be more informed before buying and many will know that power upgrades are very very expensive on this car. Best to get it with the most power available for each model year from the factory. It's a sports car afterall and power is not the be all and end all but its indeed relevant.
So not buying a 3.2 could cost you money. It's a strong possibility.