My birds prefer the flat roost. I had both for a bit in my old set up, and none of the birds went for the round. But they may have chosen it for location, too. It may have had less to do with shape after all!
I had my first roosts above an isolation pen, about 30" up. They had a ramp up, but they just chose to jump. That ended up causing foot injuries for my big Cochin and Brahma. So my roosts are only 6 an 9 inches up. No more foot problems! They're still above my nest boxes, but my dang silkies are always in the boxes because they are always broody.
I had my first roosts above an isolation pen, about 30" up. They had a ramp up, but they just chose to jump. That ended up causing foot injuries for my big Cochin and Brahma. So my roosts are only 6 an 9 inches up. No more foot problems! They're still above my nest boxes, but my dang silkies are always in the boxes because they are always broody.