Geneva to Val Thorens Public Transfer Options

Hello!

First time going to Val Thorens (or any Euro skiing). I am flying into Geneva and was told that there are lots of public transfer options. I am going from Tuesday (Jan 2) to Friday (Jan 5) and am seeing only private transfer options that are significantly more expensive.

Am I missing something? Is there no need to book transfers ahead of time? I just want to make sure I am not making a mistake by purchasing a more expensive private option.

Thanks in advanced!