Just on that point Ray;

At the detailing clinic we all used the meguiars random orbital they offered. When Dan went over the panel quickly just to even everything out, he used a proper professional one worth about double and you could see that it just gave out better results. You're right, it does basically come down to build, features and strength/capability, but it usually works out that the more expensive ones will be the ones with better features which in turn give better results.

At the end of the day, buy something you can afford and work with it. You'll get results you're happy with every time, if you practice