I would like to start accumulating a list of reason why some look for a service, I hope this will help others in understanding the reason for choosing one service over another.for example for this one:

Why would a VPS be ideal for you?

VPS allows a person to have root access (like they would get with a dedi) to install scripts that require root. Also, they would have guaranteed resources to do with as they please. VPS allow flexability as well. Shared/Reseller limit what you can do, install, etc.

A virtual private server (VPS) separates you from other customers on a physical web server, running on a copy of its own operating system, but it shares CPU and RAM resources of the physical web server with other VPSs running on that server.

In a VPS, a single physical server is partitioned so that it appears as multiple servers. The physical server boots normally, then runs a program to boot each VPS within a virtualization environment.

A dedicated server is better then VPS. Because it is a physical box and not Virtual. So I would go the dedicated over VPS.

VPS is considered to be best intermediate platform for users level between shared environment needs and dedicated server.

Even if you don't require root access, there's much to gain from a VPS. Isolation ensures there aren’t hundreds of other sites bogging down the server and guarantees your site performs to capacity 24/7. VPS can also in some cases be a much better solution than a dedicated server. Not only for the lower cost, but also the ability to burst at much larger allocations.

The only downside I see most with VPS is that the providers offer equal share of the CPU & from what I've seen that's a large reason many go dedicated rather than VPS.

VPS allows you to get a customized server to match your needs, you can compile the services with the modules you need for your customers, you completely own the server.

VPS are good for there money but if your good you will have computers at your house that are your servers. I don't have servers at my house for Cyberworld Hosting by the way. But you can always have a backup server or two if your servers goes down.

Reasons for VPS:

High uptime - VPS's can be migrated on hardware failure.
Dynamic - Upgrades/downgrades can be done realtime with little or normally no downtime.
Price - Normally alot cheaper than a dedicated server of a similar spec.
Security - Your not sharing the OS/Programs with other users like with shared hosting.
Control - Full root access, need I say more
Backups - You can backup the entire OS and config not just your files.
Custom - You can config the severs spec to your requirements no point in getting 10TB of B/W if you only need 500GB is there?

Just a quick list from the top of my head.

Good points Zanyhost

That's a good list Zanyhost and I totally agree with you.

Besides root access and general isolation, the fact that a VPS offers guaranteed resources is a big boon in comparison to shared hosting.

With VPS you can upgrade resource with a click of a button, be it RAM, HD space or bandwidth, some even allow you to downgrade on the fly.

A VPS would be good for me due to the fact that My company has a lot of clients and information for that reason, I have one VPS just for my clients and another VPS for personal information on my clients meaning all there stuff is on that vps such as the billing system and all. I also think a VPS is great for me because I like to have more power over my server meaning in another way that VPS have more power then Resellers.

Because VPS sucks and I do not want a smoothly website.