I've found both to be invaluable. Used the e-locker more at first, but I'm finding the Atrac is quite the piece of technology and am using it more. They were quite the lifesavers, especially when our FJ was shod with the Michelin all seasons (they were on it when I bought the truck)- it was a little over a year before the AT TA's went on and boy, did we tear the Michelins up (there were large chunks of tread actually missing when we took them off). I have an '08 so I always forget about CRAWL! Would love to be able to retrofit it.It is 4x4, it does have both and also crawl. We have had it out to test everything. It all works and I'm looking forward to using it!