Maybe I'm strange but I found the sharp corners much easier to see.
The round ones were distracting, especially the rounded arrows. I also found the pointy circle much nicer to look at.
With sharp corners you have 4 things to look at and process - each line. With the rounded ones you have 4 lines, 8 spots where a line changes into a curve, and 4 curves.
At least that's how my eyes do it - they notice the curve for each corner and that wastes time.
I tend to agree. I dislike many uses of rounded corners.
I also find it ironic that in the example diagram they use to compare squared vs. rounded corners, they use squared corners on the A, B, and C boxes, implicitly acknowledging that they are more appropriate than rounded corners in this case.
4 lines, 8 spots where line changes to curve and 4 curves
If you have to process the fact that a line changes into a curve, then why don't you have to process that two lines are intersecting, or 'changing' at a 90deg angle?
I thought about that and mathematically it makes sense, but that's just not how I experience it. The corner is "simple" there is nothing there for me to process, so I don't need to notice it.
The round ones were distracting, especially the rounded arrows. I also found the pointy circle much nicer to look at.
With sharp corners you have 4 things to look at and process - each line. With the rounded ones you have 4 lines, 8 spots where a line changes into a curve, and 4 curves.
At least that's how my eyes do it - they notice the curve for each corner and that wastes time.