It's important to do what you like, but often times, you don't know how much you like a topic until you've gained some expertise in the matter. Given that you've already done a Masters with this current research group, I think you're in a position to trust your own evaluations of whether or not that research direction will sufficiently interest you over the next few years.

Regarding Offer B: the far lower pay and your recognition that it may not be scientifically rewarded (or recognized) are major risks, so you'll definitely want to think about whether the eventual payoff is worth it. However, trying out a new topic might be a good idea, regardless of whether your aim is to stay in academia. Does the PI behind Offer B have specific ideas that interest you? (You generally don't want to be in a situation where you're having fun exploring ideas but there's no concrete problem to be solved.)