Tub if I know I like the product; more economicial, and, a sure-fire way of maintaining a greater supply of the good stuff around!
Tube if I've never tried a product; unit price is a bit more, but, more importantly, I'm not as 'committed' if I don't like the item. (tubes are also great when traveling!)
AAAAANNND this minion still accidentally clicks 'tube.' My vote is for tub not tube!
I find tubes to be more convenient, so I prefer those. But I do have tubs of cream too, namely Cyril R Salter's Essential Lime and some TOBS Rose which I might steal off SWMBO from time to time.
So far I have tubs so I voted for it...But some lines of Penhaligon's come only in tubes (like English Fern or Endymion, I think). This is probably true of other brands as well.
Tube, because it is easy to be consistent, just squirt the same amount each time without paying too much attention. I also prefer metal tubes like the Bigelow (Proraso) because there is less air entering back into the tube (or tub) and it just feels nicer overall.