Hmmmm...which is easier? Is one better with South winds? How thick is the ice? Will it be easy to clear a nice big area? I think it might be harder to decoy them in off the river but you'll see more ducks. It will be easier to convince them to sit in open water pond, but you may not see as many. I think the warmer weather and the winds today might have dented the chances of concentrating them on the river. You probably stand a better chance of any birds riding ahead of the front on the river.
Not much help I guess. But some of my thoughts.
If the ice on the pond isn't too thick, it sets up well in a South wind, and neither spot is a clear producer over the other.. I'd knock a hole in the ice and take my chances there. Here in OKC, 80% of the ponds are open. If more are froze over around you, then your pond would be a good bet. You could hunt one tomorrow and the other on Sunday. If you can do that, I'd go pond first and then river on the colder day.