Garmin now owns Navionics. I have used Navoinics as a back up on I pad for a number of years. I am currently running Navionics on the RayMarine Axiom platform. I prefer Navionics. I feel that the Garmin chart plotters are easier to use. Nothing wrong with the old Garmin Blue Charts (I believe that you mean that, rather than "blue tooth". (Unless you were using a GPS dongle by Garmin.).
I don't pay much attention to actual number of stars on a navigation program. Get hands on if you can in a West Marine or electronic dealer and see which system works best for you.
I expect that Garmin and Navionics charts are going to be very similar as time evolves.... The incorporation of Navionics with Garmin should improve the Garmin Charts.