2014-03-05 3:25 pm
Thank you for your question today. I understand how confusing this seems. All plans do have the same unlimited features. They all indeed allow unlimited domains, databases, and monthly bandwidth. CPU usage is where the plans differ. If your account pulls enough resources on the server, it will go into a warning zone, which you get a notification telling you the site has hit a specific level on the server. Occasionally hitting the limit is not an issue, but if your site grows to hit it often, then you will need to upgrade to the next level as it allows more of the CPU to be used for your account. In essense, the Dynamo plans can use the most CPU power, the Nitro, the next, and the Spark the lowest amount.
Whether the account contains a single site of a hundred, as long as it is not a high volume site, it can exist fine on the Spark plan. Accounts at this level are usually static html pages, with no Content Management Systems or running databases.
If you do want to use a system with a database, then the Nitro plan would be a great starting place. Accounts like this can handle a nice bit of traffic as long as they are optimized.
The Dynamo is reserved for those with quite a bit of traffic and/or CPU intensive activity.
While CPU usage can be correlated to traffic, they are not the same. A well optimized site can handle much more traffic than others as each action (file, script, database transaction, etc) would use less CPU power.
I hope this helps you understand the difference in the plans and why it is so hard to give any specific numbers on the plans.