Did you read what this forum is about? It's this.
The CNET to the Rescue forum is where you can raise issues about unfair practices by technology companies, call out misleading advertisements, and talk with other users and CNET editors about these issues.

Your question is about something else, I think.

Alas, we have no forum about GPS-devices. So all I can say: find a trusted shop and ask the sales person. Find another shop if he can't explain the differences.

Kees