Reason you not get too much assistance here is each company has a slightly different policy and pricing.
I personally have the option to purchase I have to ring them up when get my option to renew and they will give you a potential price which is then confirmed a month before lease ends. - All my previous cars that have gone back have gone straight to auction.
If consider buying, check a reasonable amount of similarly specced cars at same year and mileage and see how compares.
think everyone can make a case for keeping or changing due to variances in how the deal works for them, so there is no right wrong answer to come from here, other than do your diligence on purchase vs another lease.