If mileage scares you, check
this thread out.
In my opinion, (assuming proper, regular maintenance)
age is the enemy not mileage. I would consider both 97's to be of the same strictly based on age.
From there, it comes down to your plans with the NSX. Do you plan on driving the NSX much? If yes, get the higher mileage one, as you won't see your invested $$$ slowly tick away with the odometer. If no, and you plan to re-sell in a few years when you're bored (if that is possible), then get the lower mileage.
If it were me, get the higher mileage. You'll need the extra $$$ for maintenance/repairs/replacements
no mater which you choose. They are both 17 years old after all! I can personally attest, that a NSX with less than 12K miles looks like nothing else. But, a well kept NSX with 10x it's mileage can be kept looking just as fresh.
Good luck, and post here with your decision!
Lucas
Edit: To answer your thread's question. No, you should not be (assuming regular maintenance was performed).