What the two guys said above but there’s more to this than an easy, “It’s an easy *** more hp and TQ.”
You would have to equalize both pistons to use one head and that alters the game with the head altered. Even if you had two heads modified to accept a flat top and then a dome, the test results could not be considered equal. Nether piston can not take advantage both heads.
The best way you can call this is to say the domed piston will give X amount more compression (Lets pretend 1 point.) which would equal 3% on most builds of a high performance nature. But only that narrow window. That number percentage changes with each build. The weaker the build, the less difference in power and the reverse, more power in a stronger higher HP build.
The question is splitting hairs in the wind while at full gallop. And your cutting tool is a baseball bat.
If you have open chambered heads and need a high compression ratio, then get the domed slugs and be done with it.