Interesting research by Agrifirm compares the results between Dutch robot barns in 3 systems: non grazing - grazing less than 50 percent grass- grazing more then 50 percent grass. Here you see that income is practically the same.
However, we expect that the longevity on grazing farms is longer then on non grazing farms! You decide if you let them out again... It's a bit more work, but long term gain and methane reduction due to less youngstock and more older, feed efficient, cows.