A very outside perspective here, but from familiarity with a white settler colonial context (New Zealand) which is deeply mired in neoliberalism and whose mainstream left has never broken away from Third Way politics in the way that UK Labour has (yas Jacinda Ardern qween, but also blergh). BUT it seems, given the particular media and social dynamics in the UK especially, that literally any Labour leader would be torn to shreds regardless of their political leanings. I think the destruction of someone as benign as Ed Milliband is rather conclusive in that regard. Because of that, I think you should just choose whoever delivers better policy, because no Labour leader would ever be ~electable~ in the current climate. So between a more palatable, centrist leader with more Tory-lite policies to boot, and a supposedly very unpopular leader with policies that mark a cleaner break from both the overall and centre-left consensus in decades (and are actually, y'know, good), the choice seems... simpler.