Those two things are equivalent.
I am in no way trying to say that this can not be dangerous, but it's different from what we would usually call rootkits.
For instance, the remove-item commandlet, its description goes like this "The Remove-Item cmdlet does exactly what the name implies: it enables you to get rid of things once and for all. Tired of the file C:\Scripts\Test.txt? Then delete it"[1]. No UAC prompt. Bingo, let's start erasing this annoying C:\Users\Username\Documents.
And this is only one example, give me 1 hour and I can find several ways to fuck up your computer with a powershell open :-).