It seems like $$ is a prominent factor in your friend's decision.
Over 5 years, let's say he would drive both cars 40k miles. You will be spending at least 12k-15k on the NSX. The s2k will require basically no maint. except maybe a set of brake pads, oil changes, and tires [which it doesn't eat at NEAR the same rate as the NSX].
So you have cost of car at 30k even after taxes for either + annual insurance costs plus 3k in maint for NSX and 1500 on the S.
Once you figure that out, I'm going to assume over a 5 year period that will roughly at least 7500 in maint. extra for the NSX and at least 2500 in additional insurance costs [only assuming it's 500 more annually as the s2k isn't exactly cheap].
Note this doesn't take into consideration say, if you had to do a clutch job AND timing belt job during those miles.
Doing rough calculations this brings the s2k to 10k over 5 years to own stricly regarding keeping it on the road.
The NSX will probably drop 3-6 grand over that time period, mostly due to the miles. On the other side, that 30k s2k will be worth at most low 20's.
While there may be more hassle and random costs, given the depreciation factors etc. they will probably cost the same to own over 5 years 40k miles. More miles will be in favor of the s2k as the NSX's tires a lone add up quickly.
More detailed analysis can be found on this forum of actual costs.
As for fun factor, that's for your friend to decide with a test drive. He also needs to realize he'll need a garage for either, especially the NSX, and driving it through some city areas is discouraged.