Idk that you can say that with certainty. To me they look pretty even in that respect.
Miesha defeated two champions (Marloes Coenen and Holly), and two former title challengers (McMann and Carmouche).
Holm defeated one champion (Rousey) and two former title challengers (Pennington and Correia). I would also add that Holm held her own with Cyborg and Schevchenko who skillwise I would rank above anybody Miesha has ever faced.
So it really comes down to how you see their fight. I think Miesha had the performance of a lifetime that night and good for her for her comeback was awesome, but I believe Holm would beat her maybe 8 out of 10 times judging by how the fight went. You are free to disagree ofc. I was actually a big Miesha Tate fan so I don't think I am biased against her or her style.
My point is as it stands right is very subjective. I think Holly is the better fighter but certainly you can make a case for one or the other.
Now, while Tate is retired Holly is an active fighter, and if she ever beats Nunes or Cyborg than she should be certainly be ranked above Miesha.