What are advantages and disadvantages in using VPS hosting vs standard Web hosting services?
VPS ADVANTAGES:
You are more in control with the server; it's virtual, but still you can manage it as a full server. You have full root access, full control and therefore you can do almost whatever you want installing anything you like, even stuff that is not provided the web hosting plans of the same provider, you could remove the control panel and install another one (i.e. removing cPanel and install webmin or remove totally a control panel and manage the server by yourself changing manually the configuration). You could replace the webmail interface with another one (i.e. remove Squirrelmail, and install something else). You can change root Apache config https.conf and root php.ini config.
VPS DISADVANTAGES:
You MUST KNOW how to manage a server; getting such know how is very time consuming, you need to learn and study carefully. You screw up something on a VPS and you risk it being unusable, or even worse, up and running but with dozens of SECURITY HOLES. It's usually more expensive than a shared web hosting plan, but not always more expensive than a web hosting reseller plan.
WEBHOSTING/RESELLER ADVANTAGES:
You are in control only of what is already installed on the plan by the provider (i.e. cPanel for managing, Squirrelmail for web mail), even if you can still install your scripts and many third parties stuff. It's much easier to manage, and more difficult to be completely screwed up. If the server is down or there are security holes it's not your fault - you simply open a ticket and complain to the web host, who will have to take care about it.
You can rewrite also Apache config for specific folder using the .htaccess file. Also php.ini config can be rewritten on a per-directory basis because most web hosts install suPHP, which lets you rewrite php.ini config using a php.ini file in the directory you want it to be modified. It's definitely cheaper.
WEBHOSTING/RESELLER DISADVANTAGES:
If you want to change something at an higher level (like changing the control panel) you can't. You can NOT change root Apache config https.conf and root php.ini config.
Anyway there is still something missing here, and I'm missing it too. Many hosts are now selling FULLY MANAGED VPS; according to their policies these type of plans have the advantages of WEBHOSTING/RESELLER because if you screw up something, they look at it and they also prepare the server for you. It seems you don't require so much know how, but simply must careful not to put your hands where you shouldn't.
Actually I tried to ask a similar question on serverfault you can find there also links to other similar questions that might help you too.
IMHO I don't understand what's the catch for some hosts to push the VPS against the WEBHOSTING RESELLER plans. Some hosters are even selling FULLY MANAGED VPS at CHEAPER prices than RESELLER plans. It seems bizarre because if I buy a VPS I'm probably going to open many more tickets to ask this & that and to ask them to fix/change something for me compared the the amount of tickets I could open with WEBHOSTING RESELLER plan.