SA is generally a sculpted profile, where keys up toward the F row get taller and more angled, and arc back as you approach the bottom row. Row 3, where you can find the return key on Andi keyboards, is a relatively flat profile. You can find sets that are Row 3 only such as SA Ice Cap.
XDA is a flat profile all around, though the top of the Cap isn't as cupped as SA. You get a flatter key feel with more surface area.
Sound is night and day, however. XDA is relatively thin PBT and doesn't sound as nice as SA.