Depends on how much you value increasing the spawn rate over overall QP gains. On average, there's not much of a difference between the two setups, but, as manafusion has pointed out, some people prefer guaranteeing the spawn rate with a lower overall bonus more to prevent the bad case of no rare spawn with higher overall bonus.
I posted the math earlier, assuming that 1.5M is the average QP yield before factoring in rare spawn and QP bonus, but I don't know what that actual number is.
I will say that, for FEVER quests, I'd take guaranteeing the rare spawn over higher potential since you have a limited number of FEVER tickets. However, since I've never done the FEVER fight, I don't know if higher spawn bonus even matters.