These are the same navigator in two sizes. The routing database, the truck profile and the low bridge warnings are identical, so this is a question about the glass and the space on your windshield.
The verdict up front
Buy the 6 inch unless windshield space is not a problem. A 7 inch screen is genuinely easier to read at a glance, and glancing is the whole point of a truck GPS. It is also a bigger object suction-cupped to your windshield, and in some cabs and in some states that becomes an obstruction problem rather than a preference.
At a glance
| OTR710 | OTR620 | |
|---|---|---|
| Screen size | 7 inches | 6 inches |
| Truck routing | Yes | Yes |
| Bridge heights and weight limits | Yes | Yes |
| Truck parking data | Yes | Yes |
| Windshield footprint | Larger | Smaller |
| Price | Higher | Lower |
Choose the OTR710 if
You want the larger display and you have a windshield that can carry it without blocking your view. On a 7 inch screen the next-turn instruction reads in a single glance where the 6 inch version sometimes needs two, and over a fourteen hour day those glances add up. It is also easier to read in bright sun.
Choose the OTR620 if
Space is tight, or your state is strict about windshield mounting. The 6 inch unit does exactly the same job for less money and takes up noticeably less of the view. If you already run a phone mount, an ELD display and a dash cam, adding a 7 inch navigator on top can genuinely crowd the glass.
The thing neither one fixes
A truck GPS routes you by the profile you enter. Enter the wrong height, length or weight and it will confidently route you under a bridge that will not clear. Set the profile the day you buy it, check it after any equipment change, and treat the routing as an aid rather than as authority. The signs on the road are the authority.
These comparisons are drawn from published manufacturer specifications and the general consensus of owner reports. We have not tested these products side by side, and nothing here is legal or compliance advice. Confirm current rules with FMCSA and with the states you run.
The wider point of this comparison, that the dezl line shares one routing engine and differs mostly by screen, is worked through in our Garmin dezl OTR620 review and our OTR720 review, which is the current 7-inch model.
