I don't get why so many compare these two, they're practically nothing alike.

It's because they are both the least favorable amongst children so are always paired up.

They are somewhat alike. Both are indesicive, confused girls. Thats about it

they're as much alike as Jasmine and Aurora are

The only thing they have in common is always getting left out of merchandise.

I copy what I wrote in my link:

Surely, there is one thing that unites these two princesses: the indipendence. The other Disney Princess Movies are concentrated mainly on a love story (except Aladdin) and the princesses are closely bind to their own princes or completely dependent; but Mulan and Pocahontas are independent from their men. They think more about how to save their people and avoid useless deaths. In these two movies the love is in the background because they show more the storng personality of the main character.
Moreover, both have a good relationship with their fathers.

Both are attached to their roots. Both are selfless, both have insecure and demure side without being extremely demure.