The short answer is . . . it depends.

Cubic centimeter displacement (ccs) is the volume of the combustion chamber, which is a primary determiner of the compression ratio.

You can't tell which heads are "better" simply by the chamber voume (cc's). Remember, the engine is a system. The heads you use depend on the pistons, the compression ratio you get with those pistons, the compression ratio you want, the horsepower you want, and several other parameters.

For example, if you have dished pistons and put on 70 cc heads instead of the 60cc that came off, you'll lower the compression ratio - maybe more than you want. Alternatively, if you remove 70cc heads and install 60cc heads, the compression ratio will rise - again, maybe more than you want.