Refer to this post here Adobe - Adobe Reader download - All versions to see detailed differences between fees of PayPal Personal, Premier and Business Account. There you can find some additional information about other companies.
But in a nutshell, apply to Premier or Business Account only if you plan to receive more than 500$ per month.
In my opinion unless you don't have any serious investments in PayPal, it would be always better to stick with personal account. And once your limits for personal account are almost exceeded then it would be a good time to upgrade to the merchant ones.
The big difference is that under a Business Paypal account, you are using a Business name instead of your own personal name. So when someone is sending you a payment/money, they are sending it to your business's name, not your name. You are the owner of the account though.
Personal accounts will not be subjected to much fee. But the business account can have unlimited sending and receiving options. The fee amount will be huge. There are lots of features attached in business account.