Truman wasn't even told about deaths in those numbers. There were really no alternatives presented to him; it wasn't how it was framed at all. There were several alternatives floated at the time, but not at the level of Truman — they were discussed at a level beneath him (e.g. the Secretary of War and the Interim Committee). Truman himself only saw the results of the lower decisions.

Truman really made no decision on whether to use the bomb at all. It was a foregone conclusion. He did make other decisions relating to it, though. The most important two decisions he made were reaffirming Stimson's desire to bomb Hiroshima and not Kyoto, which Truman thought was a large moral choice (a military base vs. a city — it turns out the distinction between the two cities was less than I think he realized), and he chose to stop further atomic bombing on August 10th (and affirmed that any further atomic bombing would need his explicit permission, a decision that had large postwar and Cold War consequences).

But the narrative that Truman chose between bombing and invasion is wrong. The plan was to bomb and invade. The "decision" narrative was only added after the fact as a way of justifying the slaughter to the world (and maybe, arguably, to himself), making it appear like a difficult and deliberative "choice" rather than just an option eagerly exercised.

For a very even-handed take on Truman, and what he did and did not choose, see J. Samuel Walker's Prompt and Utter Destruction, which is probably the most "balanced" Truman and the bomb book out there (he isn't pro- or anti-, unlike most of them). My work on Truman and the Kyoto decision is currently moving through peer review, but you can read an early version of the argument here.