The fridge is my original, very first piece of temp control equipment, picked up from the scratch and dent clearance at an appliance store, too cheap to pass up. By the time I added my lagering "cellar" and later a keezer I'd learned how cheap, light weight and efficient chest freezers are. The only drawback is having to lift in and out. The one option I have no experience with is the mini fridge. By the time my seemingly immortal fridge gives out, the forum will no doubt have made me an educated consumer.
(I suspect the difference between controlling ambient or liquid temp becomes less significant as the volume of airspace around the fermenter is reduced.)