Dedicated lines - the better sounding 120v phase?

Hello all
I'm sure this question has been answered somewhere within a previous thread here on the gon, but I'm not having much luck finding it..

Can someone with electrical experience give me an idea how one figures out which phase to put the dedicated lines on? As I understand it, one is usually noisier than the other, even at point of entry into the panel box. How does one test to figure out which phase is the cleaner one?

After this is determined, is it then best to put these lines at the very top circuits in the panel above potentially noisy circuits below (appliances, fans, dimmers, etc.)?

If someone could help with this, I would really apreciate it..

Typically you want to balance the load between the phases. That is the most important. If they are already pretty balanced I would go for the phase that has the least motors like the fridge - furnace on it. The startup for motors will cause minor sags and surges on the line. Others may say the phase with the least light dimmers and fluorescent lights.
Xti16 pretty much covered it I think.I would try both sides, just in case one does have something noisy on it.Dimmers usually seem to give the most noise,in their dimmer positions. An AM radio(off station) is good for checking noise from a dimmer,outdoor Mercury,Sodium lights,and odd things like the ignition in a furnace could travel enough to get both sides. Possibly air-born RF noise from something like them.Might be a 50/50 shot.