Invisible zippers are more expensive than conventional zippers -- about twice the price IIRC. And they need a special zipper foot, which is plastic, but it doesn't cost a lot and is easy to use -- and re-useable, of course. But they are worth every extra damn dime!!! ---> Plus, I really like the way they look much better than conventional zippers -- so that's a no-brainer for me!!
There are some garments -- like jackets where the zipper detaches at the bottom, and other pieces where the zipper is part of the style / decoration -- where they wouldn't work ... but I'm not into trying anything as fancy as that. (If your mom is able to do that sort of work ... and teach it ... wow, I might take classes from her!! )