I wouldn't call it a moat, but I would call it a noticeably better model. Subjectively, for my own work, I would rate the top models Fable > K3 > Sol.

But it's not like Fable is so substantially better than the other two that I would be seriously impacted if I didn't have access to it anymore. All three are amazing models, and of the three, Fable is the only one that regularly triggers refusals.