I'm with OR. I've been at WI's top Mathews Dealer since the Z7 came out, and there are no serious or constant issues with the AVS system. Occasionally a "bad batch" comes thru the pipeline, where a machine setting isn't correct for a small run of bows, but that's manufacturing. I don't know what you read on AT, but those are far from facts. I like both bows. Depends on your preferences. I think the XS draws rather comfortably and I love the draw stop. For a mainly treestand guy, that'd be my suggestion. The ChillR will give you that stability up front, and if you like a draw stop feel the Rock Mods are damn nice in an 85% or 75% let off. Gives you better speed. Not as maneuverable in a treestand guy, but if you're spot and stalking mainly in open conditions you're good either way. 33" ATA isn't exactly cumbersome. But as guys have said, if you can shoot both, do it. Best way to make your determination. The bow generally chooses you.
Don't get too caught up in speed, either. I find the guys who say speed kills often miss faster.