The higher ratio increases the spring load on the valve by the change proportion. A spring using 1.6:1 will increase the open load by 6.7% (1.6 ÷ 1.5), a 500 lb. spring becomes 533. The closed load won't change.
The 1.6:1 rocker will also increase the load on the tappet & lobe in the same proportion. The 500 lb. spring was 750 lbs. with the 1.5:1 rocker, becomes 800 lbs with the 1.6:1.