Because at £349 its not that expensive at launch, id rather have a year of fun with it, that save £50 12-18 months from now.
Even if your just playing the same multiplat games, for the sake of saving £50 in the future id rather have, better graphics, better online chat, better controller, super fast OS, access to the 4 games already given away on plus.
Plus Infamous graphics wise is just drool, if that is a gen 1 game, bring on the next wave!