I don't think we can know who will be better or worse off, although a lot of arguments that the EU depends on the UK more than vice versa seem to take percentages more seriously than absolute values.
But I'd rather gloss over that because honestly I'm not sure it's the most important question. I suspect that the balance of trade was not uppermost in most Leave voters' minds anyway, so demonstrating that we do indeed stand to lose out might not affect them much if the longer-term aims (of, say, loss of ECJ influence etc), are still achieved. From my own point of view I'd be more concerned about the net change anyway. If the UK benefits, but the EU loses out at a greater scale, then it seems a monumentally selfish act on our part; nor would I wish to see the EU better off in such a way that the UK is crippled as a result.
Hopefully, it will be possible to find a way to make both the UK and EU better off, something I hope was the aim of Brexit all along.