I have seen both, though I would say more often than not it is going with the wind. But, I also prefer to troll with the wind, boat control is better and you don't have to be on the wheel or tiller every second. So that could skew my stats too. Current has been a player some days, even with the high release on Oahe you can feel it at times. I think the only true way to know is to have an underwater speed device, they make them but it's just another thing to have on the boat. But certainly there have been days where one way or the other worked much, much better.
One day we were north of Mobridge and it was blowing hard from the NNW. We were drifting a section and cranking it back up, catching walleyes both ways. We were going over one of our smallie spots and busting big fish every time we cranked over it into the wind. The biggest Oahe smallies of my life, several over 19". Trying to run a tiller kicker into 4' waves and 30 mph wind with a 19" smallie pulling you straight under the boat with a 5' shorty rod is an experience I will never forget. Those smallies only bit going into the wind, never caught one going with it!