I like both but I do have to say that with enterprise class systems (8CPUs +) the scalability of SQL Server could become a problem. I would love to hear the experiences of others who have seen workloads from 40,000+ concurrent users.

From what I’ve seen with these larger systems you have to buy one big supercomputer and make sure to have extra slots for CPUs, memory, and additional fiber cards for scalability. With Oracle you just go the two midrange node RAC route and add one additional machine if you need to scale further.