If you know enough about the car your buying and are a good judge of character then its often good to look at private sales.
Often people need money and want to sell their car to get back some of what they've payed, not a dealership adding their amount onto it.
Other benefit of private sales is the previous owner; if a true skyline liker, will have fixed all the little things that often come with a dealership bought car, saving you money anyway.
I beleive warranties are all Bullshit, theres so much fineprint and had so many friends with warranties that didnt do what there supposed to.
Like i said, if you know the car your looking at well, and can get it checked out, then go private sale.
I did, saved heaps No problems that havent been caused by me eheh