The advantage of using Google Analytics is that every single person you hire understands it. It’s pretty narrow in its focus--it is more web-oriented. Our product is Android, Native and Web so we need more than one tool.
I think that the more successful an email marketing tool is, the more it gets targeted. Gmail and other mail services are very careful and sometimes they block emails sent out from tools like MailChimp. Overall, though, it works pretty well.
Justworks is really easy to use. I have a contractor for HR but with Justworks, I can pretty much do it myself. The problem in the US is that you have to abide to the rules of each state if you are employing people from different states. Justworks makes it easy.