You could think of the sites that share your server as your roommates; there's really not that much separating you from them. Sure, you can close the bedroom door, but they can still cause nightmares for you in the kitchen and the bathroom. In web hosting terms, all the sites share a single server's resources, so huge traffic spike on Site A may impact the neighboring sites' performances. It's even possible that another site could take down the shared server altogether, if it crashed hard enough.
You are made to choose from a selection of templates and later get to edit them to your liking. But not everyone enjoys this! Some people prefer to have more customization and perhaps use a different content management systems like WordPress. For these people, a website builder is not a preferable choice, as they won’t develop the skills needed to make a professional page.
VPS plans are similar to shared plans in that both feature multiple websites hosted on a single server. However, VPS plans maintain a strict separation between clients and websites when it comes to resource allocations. Your site gets its share, and no one else may use your resources (conversely, you may not cannibalize the resources allocated to others' websites either).
Cloud Hosting: Cloud hosting allows webmasters to tap into a large bank of servers that are all interlinked and designed to take over from each other if needed. In other words, if you need more resources, the cloud will provide more resources to rise to the demand. Cloud hosting is usually the best option if you want to aim for 100% uptime and don’t care how much you need to pay for it.
Migration or transfer services are often free or offered at a reasonable fee. These services help move your existing site to the new hosting provider. They can save a huge amount of hassle. Just remember that the migration process is often automated, and may fit in with the host's processes and needs rather than yours. Not everything may migrate, and you may find the organization of the newly migrated site makes for harder maintenance in the long run.