I found the same result with my thesis, and this idea still informs the way I talk about EA. Actually, considering how weak a lot of the data is on charitable giving behavior, I recall being surprised by how consistently storytelling appeared to work. Some relevant quotes from my summary of said thesis:

In the meantime, some general advice for all charities:

• Tell donors what their donation will accomplish (be specific!).
• Tell stories about individual people you’ve helped.

[...]

Talk about your beneficiaries a lot. Make them sound like nice, hardworking people who have a lot in common with the donor.

[...]

Use simple, visual language. One clever study took issue with the fact that newspapers tend to use the word “affected” to describe the people who survive natural disasters. Referring to these people as “homeless” (which is what “affected” really means in this context) substantially increases the amount donors are willing to give to them.

Interesting. As someone who was massively influenced by Famine, Affluence and Morality my hunch is that philosophical arguments are very effective for a small group of people. I don't think this should obviously cause EA to switch to, and only to, narrative arguments: maybe those convinced by philosophical reasons end up being the more effective altruists.

Nice, this matches my intuition that most people will give more if you make the reasons to give at the near construal level rather than far. I do wonder how much this generalizes, though: I would expect the effect to be much smaller if, say, you exposed people to the two stories and then one week later asked them to make the giving decision.

My guess is that philosophy is good for convincing the sort of people who will be convinced of a point in general, and narratives are great for use during specific asks, like during a fundraising event. But I'm pretty sure most people who do fundraising for non-profits already know this even if they didn't have proof; now they have a little more.