Not sure how many turns your coils have. Assuming rectified mains voltage of 240V, current through the coils in series is about 6.8A. In parallel, the total current would be 26.7A, or 13.35A per coil. So if we assume you have 1000 turns in each coil, you'd have 2000 times 6.8, or 13600 ampere-turns in series. In parallel, each coil would have 13.35 times 1000 or 13350 ampere-turns, or 26700 ampere-turns total.

Connecting them in parallel would definitely provide more ampere-turns, but the current is significantly higher. Also the heat generated would be significantly higher. Since power is current times voltage, each coil in parallel would need to handle 13.35 * 240 = 3204 watts. Not unreasonable for short duty factor.

Given the higher ampere-turns generated in parallel, I'd do that if you can safely supply the current.