The wine in the 6 gal carboy will quickly turn into vinegar and be undrinkable. The bottled wine will presumably have sediment that settles out. If it's not very cloudy, it might be fine if you wait for the sediment to settle and pour it through a coffee filter. Another use for it might be to top off another batch of wine that is equally cloudy and that you want to transfer to a carboy of the same size. But if there is more than a little sediment, I'd just pitch it.
I use two carboys of the same size and fill the difference with marbles or finished wine of a similar type. Some people keep containers of various sizes. But there will always be some wine that you lose when you rack.