Most of the keycap profiles we talk about have been around for many years or at least have their roots in decades past. That's not the case for XDA. This profile only came about in the last 18 months, and it offers a cool alternative to DSA for fans of flat profiles. This is an excellent time to talk about the profile because there's a particularly attractive XDA set up for order on Massdrop.
XDA keycaps are unsculpted, so there's no difference in the shape from one row to the next. Not everyone likes typing on keycaps like this, but it's something of an acquired taste. Like DSA caps, XDA makes it easy to cover even weird custom boards because you don't have to worry about row profiles.
So, XDA profile is similar to DSA in that respect, but they're otherwise very different designs. XDA caps have a less aggressive taper from top to bottom, making them a bit more boxy with more surface area on the top. The caps are also a little taller than DSA—roughly the same as a middle row on Cherry keycap sets.