[Perfectlap]

My general Porsche advice always buy the S engine for the model you're considering. Often Porsche make cuts not just on displacement but on build materials as well. The value of any Porsche basically boils down to the engine. Without a running engine the rest is worth shockingly little. Its basically the only reason Turbo and GT3 Carreras are the only Carreras since 1999 that are worth anything near their original base prices. And obviously the build quality of these engines are on another level as they are race-proven and not just street versions.
With a 986 S engine you are getting materials that weren't even used on early base Carrera engines the lack of which has lead to engine failure in many (allegedly) gingerly driven cars.

And the other issue is that today 250 HP is not as much power as it was 11 or 13 years ago. For the street, today that level of power is really entry level for a street driven sports car at this weight. The early 2.5 Boxsters were very light, particularly with a few well placed upgrades(near racing level weight of ~2,500 lbs.without ripping out the interior wholesale ), so the reduced power on a bone stock 2.5 doesn't hold it back on the street today. But as the years went on so did the weight. IMHO at those heavier weights carrying at least 250 HP adds an extra element to the feel of the car off braking, slow corners and of course when highway merging and passing. For the track the 2.7 and 2.5 are more than enough but most Boxster drivers never go near the track so the benefit for most is strictly on the street. With used Porsche depreciation putting S and non-S engines at practically the same price points I don't see why someone would pass one up, the pros simply outweigh the marginal up front savings.