Using RAC for 25+ small to medium sized database

Hello,

My company is considering moving some development databases to a new
hardware platform. There are two proposals under consideration:

a) 5 blade servers, using VMware to create 25 virtual servers with each
virtual servers running a single instance of Oracle 10g on each.
b) 5 blade servers with each running 25 instances of a database using
RAC.

I'd like to find out if anyone has any comments as to which would be
the most efficient and what they would recommend.

Thanks very much.

Paul

.