EC2 Large Instance Vs. 2 x 2 Processor dedicated hosting

I currently have a quad code single processor dedicated hosting with 4GB of RAM at softlayer. I am contemplating upgrading to a dual processor dual core (or quad core). While doing the price comparison with the reserved large instance in amazon, it seems the price is quite comparable to similar dedicated hosting (maybe ec2 is little cheaper like to like).

Anyone has any other point of view or experience that can shed some more light on this? I want to keep the server running 24 x 7 and my concern is the processor speed (not sure what is amazon's computing unit capabilities) and RAM. For hard disk, I guess I will have to use the elastic storage to avoid loss in case of server breakdown!

If you want to have a server running all the time I usually find the dedicated servers cheaper than cloud ones. In the cloud you pay a bit more for the dynamics that you start and stop server whenever you want.

As for ECU. That is a pity that Amazon does not say how they actually measure it. There is a pretty decent try to measure what it means with multiple benchmarks in this article. But they ended with strongly non-linear scale. Another source tells what ECU is directly proportional to UnixBench - first question on this page. Actually the second link is for service that makes comparison of prices in cloud computing. You may find that Amazon may not necessary have the cheapest CPU. But you should be careful though - the CPU measure is based on the mentioned ECU measurement, which not necessary reflect later actual application performance.