OK, This is a Class A forum, but they come in many sizes and shapes. What you have, what you think is important and what you need all matter. As I have often had a job description that said "Navigator" I get asked about this one a lot.
They all have errors in their charts.
They all make mistakes, many are due to the data that they hold.
Bigger is usually better.
None of the dashboard size is really any good for planning. Use a real application for that S&T is gone, So that leaves Street Atlas and CoPilot. You can transfer the day's route to the driver's unit.
Best bet---
Either buy something somewhere that you can take it back without hassle or borrow a friends for a few days. Find out what you like and do not.
Good Luck
Matt