When most people think of daisy chains, the think aid climbing. Some sport/trad climbers use a single daisy to clip into an anchor, but since most daisies don’t have full-strength loops they have to be used with care. Use traditional daisies wrong — that is load too much weight on an individual loop — and you’re likely to blow out the bar tacks.
Since the PAS ($25.95) and Chain Reactor ($21.10) are full strength (that is each loop is full strength), they can be used as a single, bomber clip-in point. They can also be used as the central clip-in point when belaying in auto-block mode, which is my personal favorite perk of using these daisies. In other words, I belay the second directly off a loop in the daisy chain. (However, you cannot escape the belay when belaying the second in auto-block mode directly off a loop in the daisy chain.)
The difference between the PAS and Chain Reactor is that the PAS is made up of 27% Dyneema and 73% nylon and the Chain Reactor is made up of 11/16″ nylon. The PAS is a few loops shorter than the Chain Reactor, which means you can’t reach as far with the PAS. Thus, the Chain Reactor is better for aid climbing/french freeing. Both items are compact and easily tuck away to the side of your harness when not in use.
The primary purpose of the PAS and Chain Reactor is to simplify and add safety to the climber’s anchor system. Using them also saves time. Thus, I religiously have a PAS or Chain Reactor permanently girth hitched to the tie-in point of my harness and use it every time I climb on a rope.
The PAS and Chain Reactor are recommended for beginner to advanced climbers, even guides.