Fun historical note: Mac keyboards until the late 90s or so had the bumps on the D and K for the middle finger. In a vacuum either's a reasonable choice but going back and forth was always fun.

I got my first split keyboard, and I kept getting lost. So I took a knife, and cut an indentation on the keys under my index fingers. Works great.

I didn't care about them on my old QWERTY because I wasn't touch typing correctly, now I understand why the indentations are there.