I'm trying both to see which works better for her. Every dog is different. One of my older dogs had to use a Gentle Leader type, because she would not follow.

Depends on incentive. My dog needs a harness because using collar and leash I can control where the dog is and looks until it sees either a motorbike or a juicy tasty human ankle, at which point, all bets are off and Tasmanian devil turns into raging canine Houdini escape artist. When on a harness, he just becomes a whirling comedy circus act which results in far less bloodshed. He’s had same training as second dog who calmly sits with his collar on with an aloof look on his face watching the mayhem. I often wonder why people stop to try and talk to me whilst raging teeth gnashing lunatic is obviously conveying the message that he considers them to be a chewy snack but then humans are odd