There is no definitive answer. Lithium grease, motor oil, trick oils (vdH, etc.), will all "work" to varying degrees. I have tried them all, and guess what? They all sound different. Your particular set-up will dictate which one works best. The thicker ones (grease), will be quieter, but will drag the platter down more, and sound slightly less dynamic; but are probably best if you have noticeable play in your bearing well (not uncommon with VPI's)). Thinner oils will usually allow for freer motion of your platter, and sound more dynamic, and a little brighter. Oil was, for my set-up, essential for use of a flywheel. Grease was simply too "draggy" for use of a flywheel, and would cause speed fluctuation.
There is no one solution. Experiment, and see which one sounds/works best for you. Good luck.