Occam’s Razor, there are a few different ways of writing it, I like "Keep it simple" because it follows its own advice, but when talking about theories it’s better to say “Out of two competing theories, the simpler one is better”. The problem I have seen is people misuse the razor, out of confusion about what it means for a theory to be simpler.
So what is meant by simplicity of a theory, looking at the complexity of the whole theory is wrong, because the more things a theory explains, the more complex it becomes, so that leads to a theory that explains less things becoming the “better” one. It is better to look at one thing both theories explain and see which gives a simpler explanation.
For example take geocentrism and the modern model of the universe and the orbit of planets in both models. In the modern model the planets in the solar system orbits the sun and go in circles and are simply explained by gravity, when the earth is the centre you have the added complexity of epicycles and the orbit path looks like this
http://www.ottisoft.com/img/Geocentric_view.jpg. So the modern theory has simpler orbits, even though it more complex over all since it contains more things, e.g. black holes, life cycles of suns, etc.
There is also a second problem, lets create a theory called the TV theory, where everything in the sky is just an image on a large TV screen or similar object, in this model everything can be simply explained by saying it’s just what the TV screen is showing us: orbits, it’s what the TV shows; supernovas, it’s what the TV shows; sun sets, it’s what the TV shows. Occam’s razor appears to say go with TVT. TVT can explain anything very simply, but do you know what is can’t do. PREDICT. So Occam’s razor should be written as, “Given two theories, the one that can predict events in a simpler way is better”.
If TVT was to make predictions, you would have to say the TV is showing us an image of a solar system with the planets orbiting the sun, now it would be simpler to just say we are in a solar system, the TV isn’t necessary (this was the original use of Occam’s razor, to remove unnecessary metaphysics objects).
So to sum up, don’t look at the complexity of the whole theory when using Occam’s razor, look at the complexity of an aspect both theories predict.
And saying a theory explains something simpler is not a valid use of Occam’s razor, because if it was than TVT is the best theory. Predictions are the main thing that matter.
“Given two theories, the one that can predict events in a simpler way is better”.