[Apollo.]

 

This is gonna be a mouthful and probably wont make much sense, so read with a grain of salt.

I honestly dislike both of them as an option for her mate. While Ashfur would've probably not been yk a psychopathic murderer if the two of them became mates he was still trying to become mates with her under the wrong intentions. I don't think he ever actually loved her, I think he had such an unhealthy obsession that he thought it was a strong feeling of love, where as he was actually an unhinged cat willing to destroy the clans if something didn't go his way, a bit like an insane, murderous, entitled child. As for Bramblestar the two of them started off fine, but it quickly turned into a toxic relationship built on a power dynamic and distrust, and that lead to domestic violence and verbal abuse.

as for who would've been the better father to her kits, it probably would've been Bramblestar. Let me explain my thinking here; still comparing Ashfur to an entitled child he'd probably use their kits as a way to manipulate Squirrelflight into doing what he wants, similar to how he manipulated Shadowsight. He'd probably threaten to hurt them to get to her, hell, he might even have gone so far as killing one of them in front of her. He wouldn't have cared if they were his kits or not, as long as Squirrelflight cared about them he could use them to his advantage. (We can actually see a demo of this during the fire scene, he was threatening to kill the three until she told him that she couldn't care less if they died because they weren't her children, at which point he backed off and let them go because killing the three would no longer give him any leverage over her.) While Bramblestar didn't really care about any of his kits after it was revealed that the three weren't his, he never used them as leverage against Squirrelflight, he'd actually stop abusing Squirrelflight when she was expecting (which is kinda worse in a way?). Anyways, this is just my opinion, and seeing as Ashfur was never the father to any of her kits we can't know for sure how he'd act, all we can do is theorise.

So no, I don't think that Ashfur would've been a better mate, I think that he and Bramblestar would've been around the same level in the 'bad dad/husband' category, neither is better than the other. (yet again, just my opinion)