Have all three listed and two XLR's. I have a review on the X-Ray in this forum and I cover why the X-Ray is my favorite. It has the best ergonomics and is the lightest of the three. Had it on the range today and shoot's lights out and, like I said it is juts my favorite chassis system. A VERY close second is the XLR chassis. Love it so much I have two. It is comfortable, tough and has more areas to attach doodads then an erector set. The AICS is nest on the list. It is a heavy chassis and I use it on my heavy rifle. It is a great system but not as comfortable to shoot as the X-Ray or XLR. Rounding out the pack is the McRees, and again, nothing bad to say about it. It is a great piece of kit, but personally I prefer the feel of the others. As far as price, the AICS is most expensive then the XLR and McRees about the same price and the X-Ray. Next is turn around time between order and having it in your hands. AICS is fastest as most of the time they ship same day. McRees are quick and I had mine in 10 days and the XLR's are about 4-6 weeks. The X-Ray is not out yet (got mine early at SHOT) but when it is I am sure the turn around will be fairly quick. Last customer service, a three way tie with KRG, XLR and McRees with AICS falling behind. I can call Kyle about my XLR and he calls back in 5 min, same with Justin with KRG and McRees is noted for there CS as well. Who do you call for AICS? The vendors do what they can, but they are vendors.
So there is the run down, and again favorites are subjective. The X-Ray is a narrow edge of the X-Ray and that is tenths of a % over the AICS and the McRees. In honesty I don't think you can go wrong with any of the above. I posted a personal favorite because it fits my wants/needs and is more comfortable for my frame, also I shoot without my thumb wrapped around the grip and the X-Ray provides the best thumb shelf.
Sully