The point of change in momentum (the bottom when it comes to squats) is the point that generates the most resistance.
At parallel, the knees are taking the largest percentage of the load as possible.
Hence it follows that squatting to exactly parallel is not adviseable for longterm joint health, as you are essentially placing the largest load possible on the weakest point possible.
Rather, at least slightly below would be preferred. This will allow the hamstrings to take over that extra load during the momentum switch.
Going even lower than that will further engage the glutes.
The option between those two is up to you as to where you want additional growth. Make sure you base this on balance rather than aesthetics. Many guys get so wrapped up in a fear of a large butt that they neglect it entirely & then end up injured that one time they go too low by accident. To choose between the two, you need to know where your genetic strengths are & how much accessory work is being given to either one.
Squatting above parallel, on the other hand, may not be so much a risk to the knees as going to parallel, however you are artificially raising the amount of weight that you can actually handle.
Thereby, the spine becomes the bottleneck of the movement when it comes to strength. You are throwing on loads to your back that it may not actually be able to handle, which can be very dangerous but also has a high genetic factor when it comes to that risk (some people just naturally have very strong backs... though probably 95% of lifters are weaker than they think in that area).