How do hybrids (half-humans and half-ghouls) rate in strength compared to normal ghouls? In the anime series, there are several types of hybrids: artificial half-ghouls like Kaneki, biological half-ghouls like Eto and half-humans like Arima. How are they supposed to rate in strength compared to regular ghouls? Are they stronger, weaker or have equal strength? Is this stated in the series?
Biological half-ghouls are extremely rare. However,


in the Tokyo Ghoul universe, they are considered an urban legend and their strength are supposed to be superior compared to regular ghouls 
To cite examples of their strength, Eto was an SSS rate in her Owl form and S rate without her Owl form; the Underground King waged war against humanity, prompting the creation of the CCG and V;


Artificial half-ghouls are similar.


Looking at the list of successful artificial half-ghouls here, one can see in the manga that their abilities are way above a normal ghoul
While not stated in the manga, I think what affects their strength is the abilities of the ghoul that they were made from (only Rize and Eto was used by Kanou to make artificial half-ghouls, who were at least S-rate ghouls)


Half-humans raised in the Sunlit Garden


have highly developed physical capabilities. While not elaborated upon, I consider their strength still superior to normal ghouls as most, if not all, of them were highly distinguished investigators (as seen in their membership in Arima Squad)


Against each other, it would be difficult to rank hybrids as there are a lot of things to consider. However, even without official information on their ranks, strengths, etc., biology tells us that hybrids have improved or increased function of any biological qualities. (Heterosis) So, it would be safe to say that hybrid ghouls are superior to normal ghouls.