If you want to play it safe, go with the 303's. In the end it really depends on the day, there are definitely days out there when a 404 might be too much for many. I remember a CSC training camp where I was descending behind Bjarne Riis (a pretty decent bike handler I would say) and he needed all the skills he had to keep his 404's on the road. He would get blown sideways several feet at the time, quite nerve-wracking when your right on his wheel. I was extremely glad those 404's were not on my bike.
That said, the key of the problem would be the front wheel, a 303 front with a 404, 808 or 909 rear would be a lot easier to deal with.
Gerard Vroomen
3T.bike OPEN cycle