Convenience of inserting external data (products) as Drupal nodes
IMHO, you have this choices :


Use the Feeds module to import data to nodes via CSV file, and you can use the powerful Views module to list all your product, or develop a simple module that can do that.
Use can develop a module that build entities based on your tables, with this approach, you can use your database without creating nodes/terms or other stuffs, but you need to create an admin interface to manage all your tables
If you plan to sell your products online, try to use Drupal Commerce, and import with Feeds module