There are pros and cons to each way. W / S is more intuitive for beginners, but A / D is a lot easier to control given you have gotten used to it or have more experience with games. Perhaps a middle ground would be using the mouse to control, or using space bar to go up and having it go down automatically. W / S may be a good idea since in a game jam people are only going to play your game for a little while, although when I was playing I found it necessary to move quickly so perhaps adjustments should be made to how far you can see ahead or the movement speed or something else that makes it a bit easier if you want to use W / S.