I think if I had 10k, I would buy a minter of a 350z that’s been well looked after. With the change left over, do as you please, keep it looking mint condition and ‘tastefully’ modified (retrimmed steering wheel, exhaust etc). I’ve said for the last year they’re creeping in price and will continue to do as they slowly get written off, finer examples are hard to come by.
I haven’t driven a 370z, but chose 350z as others said they’re more ‘raw’.
Either way both are great cars and everyone will tell you their opinions, but the only one that matters is yours!