Personal gratification is what it's all about. You said it well, it's not all about money. I would lean in the direction of my passion without a thought.
If the system works, your Delta interview may reveal your indecisiveness and lack of passion for just being a pilot flying from A to B and you might not get a choice at all.
It's not for everyone. No matter how eventful and demanding a flight may be, when successfully concluded and the brakes are set, no book has been written, no bridge has been built, no bad guy has been brought to justice and there is nothing to show for it. For me that's great, I'm fulfilled by doing the best I can at what I do, get off of the airplane and go have some fun whith what it allows me to afford. That's plenty for me but I think it would really suck for one who needs to be more creative for their fulfillment.
You should be proud of your work that put you in a position to have such a dilemma. Your questioning might be indicitave of A and B flying not cutting it for you.
Best of luck to you. Please keep us posted.
CG