A magnetic mount sounds like it shouldn't work for something as heavy as a phone. In practice, the good ones hold fine through potholes and sharp turns - the trick is in a couple of details most buyers skip over.
It needs a metal plate for your phone to grip, if your phone doesn't already have one built in. Most cases without MagSafe or a built-in metal ring need a thin adhesive plate added to the back first. Skip this step and even the strongest magnet has nothing solid to hold onto.
Placement matters more than magnet strength. A mount on the air vent is easy to install but gets knocked around with every vent adjustment. A dash or windscreen mount with a proper adhesive base is more stable, but check your local road rules first - some states restrict where on the windscreen you're allowed to mount anything.
A thick phone case weakens the hold. Magnetic strength drops off fast with distance, so a bulky protective case or a wallet case with cards in it can be enough to break the connection on a rough road. If you run a heavy-duty case, look for a mount rated specifically for that extra thickness rather than a standard one.
A wireless charging mount is worth the small extra cost. Once you've got a magnetic mount in the car, upgrading to one with built-in wireless charging means your phone charges automatically every time you dock it - no cable to plug in each trip, which is genuinely one of those small conveniences that's hard to go back from once you've had it.