Oracle claims that one of their CPUs is equivalent to two vCPUs. If this is true, then their rack rate is a little less than EC2 per instance hour, and block storage looks like it's half the cost.

But with Amazon, all my instances are either reserved or spot, so I'm paying far less than rack rate.

It all comes down to price per performance. You can't tell anything from these headline numbers. But since we're prohibited from disclosing results of any performance testing, there's no easy way to know.