We left the A28 some way north of Rouen and went via Yvetot, both ways. Coming back Sunday after the race other members of our party used this route as well and reckon that after Rouen they were passing cars they had already passed on the way up to Rouen so the inference was that the route through Rouen was quicker.
Through Rouen is the shortest route and has the potential to be quickest but also the risk of getting stuck. So you can take a longer route and be more certain about time, or gamble on the direct route.