Following are the reasons for which one should opt for Dedicated Server :

1)  If you have large database application,  streaming media in short heavy site that needs large resources then you should go for Dedicated Server Hosting.

2)  If your site needs higher speed, flexibility, reliability and security.

3) If you want to host number of domains or websites, where the cost per web site goes down dramatically if you choose dedicated web hosting.

4)  If you need root access to your server to get complete control over all the sites you hosted on your Dedicated Server.

5)  If  the traffic on your web site is over 100,000 visits per day and want to improve your performance drastically.