It must depend how much you're sending, as I did the math last week and Xoom came out on top.
But it's no use anyway, he's going the other way.
You break even at 200 dollars. Anything less, Xoom is better. Anything more, WU is better.
Actually, 250 US dollars if you use Xoom payout in USD, Xoom charges you $8.99 with bank account based transfer.
Anyway, over 250 USD WU is cheaper with bank account based transfer with USD payout.
When calculating, you must look at your payout, and calculate your real cost, not only obvious cost. (e.g. how much would you have to wire by Xoom to get the same payout in RD$ as if you wire by WU with US$ payout)