1.5 or 1.6 ratio how to choose?

The answer is "it depends". I always choose a camshaft based on the rocker I am using, not the other way around. In other words, choose a camshaft with the lift at the valve you want with the rocker you have now. Otherwise, it's kinda a "band aid" for a camshaft that doesn't have the lift you want. If that makes sense.