I don't see the point of debating the merits of a GE when Labour can't force one and Tories don't want one and so it won't be called.
Also, given the choice between Tory rule and NoBrexit or Brexit and Labour getting in I'd prefer the former. Brexit is the most important issue right now (it will be permanent, governments change) it will hurt people forever and it can only be stopped now. If Corbyn won't oppose it then I don't want him as leader anyway.
Right now the situation is that the Brexit deadline is coming up fast and the Tories are clinging on to power but have no ideas and no majority. Labour need to recognise this and use whatever influence they have to, first, prevent No-deal, then do everything possible to mitigate the Brexit we do get - all with the ultimate aim of stopping Brexit altogether.
To me it's a huge mistake to think about Brexit in terms of what it might mean for Labour's chances - Brexit is THE thing itself.