Vacuum Engine VS Stirling Engine, Who Wins?

Q: Is Vacuum Engine the same as Stirling engine?

A: No, not at all.

Q: What's the difference? Are Vacuum Engines More Powerful than Stirling Engines?

A: Every Stirling engine has a sealed cylinder with one part hot and the other cold. The working gas inside the engine (which is often air, helium, or hydrogen) is moved by a mechanism from the hot side to the cold side. When the gas is on the hot side it expands and pushes up on a piston.

While A vacuum engine derives its force from air pressure against one side of the piston, which has a partial vacuum on the other side of it.The valve opens again in time for the piston to expel the burnt gases before the next outstroke begins.

The thermal efficiency of the striling engine is between 15 to 30 % which is much better then the vacuum engine but the mechanical efficiency of vacuum engine is much more than the striling engine.

Vacuum Engine & Stirling Engine, which you are more interested in?