There are a lot of factors that can play into the choice of one package over the other. There is no formula to determine, which one would be best. If you have an idea of how big your site will be and what sort of traffic you will be looking at, then we can give you an idea of what to go for. 

Magento sites can be hosted on the cloud, we have quite a few of them residing there. However, if your Magento site is going to be particularly heavy and rich in content, then we would recommend having a look at one of our dedicated solutions. With them we can customise the environment to fit your site's needs best, you will get dedicated resources and we can optimise the performance of your site.