For web hosting, a dedicated server is not better and faster than a VPS. Even for my personal usage, I always create some VPS on a dedicated server. Because if you are the only user of a dedicated server, it will not make any differences to run your web server or your control panel. And with VPS you can limits the resources usage when it's harder with a dedicated server.
VPS also provide some features like backup, migrations, ability to be resized quickly.
It all depends on what resources your website needs.
If you have maxed out on ram, AND your site performance is being inhibited by the low amount of available RAM, then yes, upgrading to a dedicated server with more ram. The same goes for cores, space, uplink speed, etc.
The biggest inhibiting factors on a VPS are:
Some hosts overselff resources and/or only give "shared" resources.
Disk IO can be a problem. If the host does not have adequate disk arrays in place, IO can really slow you down.
Uplink speed. The physical node will have a set uplink speed (determind by how it physically connects to the switch). All VPS's on the node have to share this uplink.
Can a dedicated server be faster then a VPS? Yes!
Can a VPS be faster then a dedicated server? Yes!
It all depends on what you have, compared to what your site needs.
With a VPS there is the added overhead on the server(dedicated) for the virtualization software. But that really doesn't seem to matter anymore. Virtualization software is so well written now that you really can't tell a difference if you are on the actual dedicated server hardware or a vps.
Agree with the previous replies. If the dedicated server configured with the more resources and configuration then it will be faster, RAM, CPU allocated will decide whether dedicated server is fast or VPS.
If you have configured your dedicated server with the adequate resources then definitely you can configure your VPS on the dedicated server.