Usually a loop is worse. Most of the coupling in the side-by-side scenario is magnetic. It is somewhat dependent on the impedances involved. If there is a relatively low impedance load on your touch system, then magnetic, but if the impedance loading those wires is high, then I would swing over to considering the E field coupling to be the stronger interferer. However, a loop with a termination resistance might still be effective for both, and you can tune the termination resistor to get the worst case effect.