RAC and scalability

Hi all, i've need some advise for resolve my doubt on RAC, because i have to sizing RAC environment in my business. Have been shows me two different solutions of RAC: 1) One node of Bl680c (until 4 CPU quad Core) 2) Two node of Bl480c (only 2 CPU quad Core) The type of choice is a valuate for future scalability, first solution