As I already sad in the post where I asked for this section masking vs earsing?

I use masking the most, just cause when i make a mistake I can easily fix it.
and it is easier to make some parts semitransparent.
last sometimes I start with masking a part away and latter on in the project, I find out it is better looking with that part still there.
I think it does increase file size and is heavier on your machine?

So tell me what do you use most and why?