so, if you would buy a village for 4, obviously buy a mining village. It's a nice plus. As O mentioned its stellar as a late game cash boost when you won't see it again. And in general, as an opening, It's overrated, don't do it unless an early 6 would be REALLY helpful.
Compared to farming village, the question becomes is the extra cycling worth an extra 2$, with any form of estate trashing (which you likely have if you are buying a village) it's rather clearly not. Late game, the vp avoidance helps but 2$ helps much, much more. Workers village is worthwhile if you don't have +buy and want it, but, often you don't need that much +buy in any case (in bridge games, where you really want +buy, +2$ becomes super useful as well, in a mega-turn, I'd probably go with mining village). With walled village, well if you really want a torturer hit.../aren't really building an engine but really don't want collision I'd prefer it. Trash it if it leads you to province, or, late game, if it will help you. As a general rule saving it till late is the right strategy unless you have a good opening.