Hey, we all have to learn somehow!
Just a few little thoughts from my experiences (mostly in compositing/VFX, but a bit of motion graphics).
I tend to use masks most of the time, for a few reasons : Firstly, they are quicker to apply than a track matte, so for simple stuff, like if you only want part of an image to show up, you can just grab your pen tool and draw away, and you’re done.
Applying a track matte takes an extra layer (which also creates clutter) and while they’re still pretty straightforward, i find it less convenient.
Basically I mainly seem to use track mattes for circumstances where I need to get a more complicated alpha – for example, using a fractal noise layer as a track matte means that the underlying layer will have detailed, varying levels of opacity… good for interesting fades/transitions, or stuff like reflections in water, where you only want the reflection to show up in the brighter parts of the water.
It’s thinking about alpha in a different way than masks.