PlantNet. I use it a lot and it works great for me.

I use PlantNet the most

Idk about "favorite," since I haven't used many, but plantfinder seems to work really well. Just annoying you have to click past the "sign up for premium!" page every time you use it.

My favorite app is called Seek by iNaturalist. It's free plus if you sign up and install the inaturalist app you can upload observations to your account to look at later online.