33 is a more refined drive, however I think the biggest factor irrespective of the model will be the modifications done.
With big mufflers its possible to end up with a quieter than stock 3" system. Another big factor will be the fuel pump which is not an issue for most because their exhausts are louder than the pumps.
I think with enough dynamat, standard fuel pump setup and a well thought out exhaust either car will be suitable.
If your not familiar with skylines i'd avoid auctions. Honestly the best place to buy one of these things is off another forum member, they are more likely to have kept up with maintenance and used quality gear.
Sucks to hear about your eyes but like you said best to enjoy your vision while you can. Goodluck!