This seems like a reasonable question to me, looking at this through a 1987 lens.
Of course, from a 2024 perspective, the difference in WAR is so great and it is a no-brainer. But if you are looking to mirror how these numbers would have been perceived in 1987 and especially given that the first baseman actually won a Gold Glove award, I think an argument could be made that he would have been chosen for the MVP award. That gaudy RBI total alone would have likely made the difference in voting in this historical context.
Sure, I would much prefer to have player #2 on my team. (Hey, I'll take them both and be very happy for having them.
)
I think I might also consider their overall popularity, reputation, personality traits, etc. to get an idea whether the voters might have had an intangible reason to favor one over the other.