Whether it is better to place a phone mount on the dashboard or the windshield depends on your vehicle's layout, local laws, and personal preference for visibility.
1. Windshield Mounts
Pros:
Line of Sight: Keeps the phone closer to eye level, which can be safer for following GPS directions without looking down.
Strong Suction: Glass provides a perfectly smooth, non-porous surface that typically offers the strongest grip for suction-cup mounts.
Cons:
Obstruction: It can create "blind spots" in your field of vision, which is a safety concern.
Heat Exposure: Your phone is directly exposed to sunlight through the glass, which can lead to rapid overheating and battery degradation.
Legal Restrictions: In many regions (and several U.S. states), it is actually illegal to attach anything to the windshield that obstructs the driver's view.
2. Dashboard Mounts
Pros:
Unobstructed View: Keeps the windshield clear, providing a better view of the road.
Easier Reach: Depending on your dash depth, the phone may be physically closer to your hand for quick interactions (while stopped).
Discretion: It is less visible to passersby, which can slightly reduce the risk of a "smash and grab" theft.
Cons:
Surface Texture: Many dashboards are textured or made of soft-touch materials that don't play well with suction cups; they often require a permanent adhesive disk.
Dash Damage: Adhesive residues or long-term UV "fading patterns" (where the mount blocked the sun) can damage or mark your dashboard permanently.
Technical Note: RFID and Interference
If you have an RFID toll tag or access sticker on your windshield, avoid placing a metal-backed phone mount or a large smartphone directly in front of or behind it.
Signal Blocking: Just as metallic tints can act as a Faraday cage, a large metal phone mount or the internal components of a smartphone can interfere with the UHF signals (860MHz - 960MHz) used by toll readers.
Clearance: Maintain a distance of at least 2 inches (5 cm) between your phone mount and any RFID tags to ensure your tolls are read correctly.
Summary Recommendation
Choose Windshield if you live in a legal area and prioritize having your GPS in your direct line of sight.
Choose Dashboard if you want to keep your windshield clear and don't mind using an adhesive disk.
The "Pro" Alternative: Consider a CD slot mount or Vent mount, as these often provide the best balance of stability and visibility without blocking the glass or damaging the dash.