Its probably been said, but what exactly do you mean by "Best bang for the buck" because that is a pretty generic term.
If you mean efficiency then there is no denying the Leaf 1500W 35H motor that Neptronix found.
If you mean power, then Crotia's Cromotor could be on the list, or their mother the QS.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=108801&p=1592811&hilit=croatia+motor#p1592811
Then there is the MXUS 3 and 5kw. Someone posted about the difference between the two.
If you just want dirt cheap, then perhaps Voilmart wins that one, $200 gets you the kit without battery. Or you could say YESCOMUSA wins, or anyone of the countless other generic hub motors sold on ebay but most of the time you have no idea what size motor those are, or how reputable the sellers really are. If your just going on some rando or where other ES members have purchased from. Could even debate if BMSBattery and their Q11 motor (DD) would win, but remember they have higher shipping prices but lower product prices.
Finally, what about sales, service and support? I'd suggest that Grintech wins that one www.ebikes.ca or EM3EV if they were selling DD hub motors.