13-14 gt

I was wondering if it's a better deal to just buy a gt 500 any year between 11 - 14 or get a gt between 13 - 14. I can get a 13 gt for around 17k to 24k with decent milage. I can get a gt500 with a similar milage for around 30k to 40k. There's also the boss 302 but idk what's the advantages of...