QAD HDX. Timing a qad or rip cord is the same one is not any easier to tune than the other. The advantages of the qad hdx is full containment even if you have to let down. rip cord will drop if you draw and let down. setting the center shot on either is the same,,its center shot alignment regardless of what kind of rest it is.
Both in my opinion are good solid rest. If your worried about having to adjust timing down the road the QAD has a cable clamp that comes with them and is very solid and does not move.
Timing of either rest, start out with the rest just timing out at the very end of your draw cycle, Most of the time this will be the spot. If you find that your set up needs to let the arrow ride longer then make an adjustment to the tension on the timing cord and have it time out a little sooner on your draw cycle.