Comparing a dedicated and VPS, a dedicated server definately has an upper hand. A dedicated server is a standalone server, wherein all the server resources are completly dedicated for your disposal. The entire server is dedicated for your sole use. Where as in case of a VPS, a dedicated server is partitioned by virtualization and VPS are created. You get much higher resources on a dedicated server as compared to a VPS. In case of a VPS, if a single node is consuming high resources, it may affect your sites performance, which won't be a case with a dedicated server.