It's no different than cars. You can have a car manufacturer making 2 engines with the same displacement and even many parts in common but one has different cylinder heads, camshaft(s), induction system, fuel system, compression ratio, etc. and one makes more power and at different RPM ranges.

You may even find RC engines that are similar displacements from different manufacturers but one might make a lot of high RPM power while the other does better at lower RPM and spins a different prop. All have their place and advantages for certain applications.