MyISAM vs InnoDB - WordPress Installation
To speak to the worth of a VPS -- yes, it is worth the money to use a VPS instead of shared hosting when CiviCRM is involved.  Certainly, you get the benefit of controlling your server environment for things like database engine changes, but perhaps the biggest benefit you will see is increased performance. The shared environment may work in the short term, but as your database and needs grow, I suspect you will hit limitations with your hosting.

See this question for reference: Choosing a VPS solution for CiviCRM