This is obviously an important decision in WDW planning. I spent months debating this. I built a simulator in my basement and gathered a group of test subjects. I made sure the cross section of the Disney population was well-represented; so mostly
ECV-riders, stroller pushers, Brazilian tour groups and Pooh-sized with food in one hand and a toddler in the other. Power analysis indicated we would need a sample size of 84 independent swipes for both left and right-handed. Results indicate that wearing the band on your non-dominant hand on Monday in peak season has a slight advantage over dominant hand on Thursdays in the off season. Results also suggested that there was a standard deviation of 14.2 seconds per attraction, indicating that the hand chosen could markedly increase time to enter an attraction and wait in a line.
With this in mind, we set out to invent a non-handed device. We removed the band, leaving just the puck. We then narrowed the puck and elongated it into a rectangle. This slim device can fit in a wallet or directly into a pocket, eliminating the need to wear it at all. We are going to call it a "Magic Card". The idea is that as one approaches the Magic Band reader, one removes it from his/her pocket and can then chose EITHER hand to place it next to the reader. We have not had the time to test our hypothesis that this device will reduce the wait time at the Magic Band reader as we have been busy with the design.