I think you could have the same luck (good or bad) with either one - really depends on the owner & maintenance history. The TT is certainly a much stronger engine, being built to withstand the TT to begin with & as I say it can easily take 500hp on stock motor. Just because it is a turbo doesn't necessarily mean its been thrashed: mine eblonged to my father-in-law who treated it like I treat my NSX - well-maintained & inmmaculately kept - sure, its driven hard occasionally but not over-driven
As far as regular maintenance costs, I don't see much difference in typical repairs or general maintenance.
I would still say hold out for a TT - almost $8K for NA seems a lot for 115K+ miles. However if you don't care about the extra performance it may not matter to you. The TT will definitely be worth more, they're in greater demand.
You probably know this, but at first glance TT easily recognizable between the two by the spoiler on the tailgate.
Ohh - they have the same crappy Bose stereo problems as the NSX i.e. the amps blow up! First thing I replaced on mine when I inherited it!! l