Perhaps quality is subjective, but saying RED cameras are low end of quality is complete BS. It is a popular misconception though - a lot of people didn't get the workflow early on, and unfortunately the reputation stuck. People were used to cameras that destructively burnt in gamma curves, altered brightness, etc. and the raw RED footage that required a little massaging to bring out the image which confused people. The advantage is that it gives you massively more flexibility for altering the look in post. These days, great colour grading software like Blackmagic's DaVinci Resolve and others is far more accessible and everybody wants raw now, so its not really much of a problem.

Arri make some great cameras too. Really, both have come so far that either can generally achieve most or all of what a talented DOP is going for.