Ah, yeah. I think you’re right, the apes give even more XP than the gorillas.
Yep, according to the Wiki it’s the grey apes that give higher XP by almost 4000 (12600 vs 16200). Both are easy to kill and found together in the same general area so Atoma can just smash 'em both. Also worth it to skin 'em for useful resources. 
I also agree that it’s better not to power level the first time through. After the first playthrough, sure, but not the first time. Enjoy the journey, it’s what CE is really all about.
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