Explorer Business, not Explorer. Exp Bus gets 2x miles on restaurants, gas, and office supplies. It strictly dominates the Explorer card, and for most people, dominates the Club Card.

The Club Card's 1.5x miles are just a gimmick. Even the normal Explorer card already earns 1.4x at 25k (because of the 10k bonus miles), which is the exact amount you should be putting on the card. No less than that, because you wouldn't meet the spend waiver, and no more than that, because there are better cards to spend on after you meet the waiver. Exp Bus easily averages over 1.5x at 25k spend for any remotely normal spending pattern.