As Chris mentioned, it really depends on what you're doing.
Dedicated and VPS hosting offer all of the advantages that Shared does not, specifically dedicated system resources and the flexibility to customize settings beyond your public html directory. Shared hosting providers also usually impose restrictions on allowed file types, minimum file permissions, etc.. and when another shared hosting client is hogging resources, your site may suffer.
On the flip side, shared hosting is economical enough to develop and test a site without the overhead expense of a dedicated server.
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