One of the downfalls to shared hosting is your website can be affected a lot more by other clients actions. If another client spams then your emails may be blacklisted because they are from the same IP.
It depends on the reliability & amount of security you’re looking for. Shared hosting can be very risky as others have described in this thread. Your site’s security and reliability depends on other customers’ practices.
Dedicated server is more flexible, but costly.
Go for dedicated only if:
1. You want complete control of the server, and want complete security for your data.
2. You have too much traffic, more than few hundred GB per month.
U can also choose VPS or semi-dedi servers.
Yes, There are also semi-dedi servers that can be used more efficient for a beginners’ usage.
1: You can control your server better.
2: You are in a better position to provide support.
3: You can limit the number of customers you want on that server.
1: More maintenance.
2: Can be quite complicating, if you do not have enough computer skills to manage it.
3: Definitely more expensive.
4: Most dedicated servers renting companies do not provide sufficient software(s) for the best use. And such software needs licenses, so you might need to purchase them.
In shared hosting,If another site is DDoS attacked then your site will go down as well. If another client installs a faulty script that hogs the CPU, your site will lag until that has been corrected. A good host will minimize these risks for you, but if the site is mission critical to your business then I would go with a dedicated server.
It really depends on what you are looking for