Is a VPS with some resources the same as a Dedicated server with exactly same resources?

Solution 1:

In the best case, it will be of similar performance (with a slight performance impact due to the virt overhead). In the worst case with a bad provider, you end up in a "up to X" situation where the provider overcommits resources and if people start to use those resources, things get slow.

VPSs are cheaper because even a good provider can overcommit (selling more resources then he really has, because in reality, most servers idle most of the time) and also because there is a big overhead to run a physical server and it's much cheaper to run one powerful server that then runs a number of smaller VPSs instead of running the same number of physical servers.