There's alot to determine the answer to your question mate. Ultimately the the biggest factor is cost.
When you say a converted 08 car. Do you mean one that's had the post 2010 front and rear lights fitted as well as a few cosmetic changes? Or it has literally had ALL the mechanical upgrades too?
If the it's only the former than, I'd not bother with that because the best things about post 2010 cars are the upgraded engine and gearbox (8 speed).