I also wonder how much of this is that shorter emails look more like a real person. I have to deal with enough spam and try-my-product emails that I delete emails at the first sent of "sales".
I would be more inclined to the shorter email which looks more like a person actually typed it.
I work for Adyen in our developer experience team. It might have been some time since you integrated but we would love to hear about your experience integrating to Adyen and how we can make it more simple. (You can reach me at directly at [email protected] or reach out to our team at [email protected])
I would be more inclined to the shorter email which looks more like a person actually typed it.