If you are looking at a semi float XD60 and a FF UD60, its a sacrifice either way IMO. With the XD60 you are getting a quality axle hand made by experts and comes with the best warranty in the business, but you are still getting a semi float axle. With the UD60 you are getting an axle that is assembly line built, really has no warranty, but it is a full float axle. The only reason you are comparing them is the cost. The best comparison is a FF XD60 to a FF UD 60. Sure the Dynatrac is more, but if you are already in position to spend $4500 on a UD60 axle, it would be wise IMO to save a little longer and pay the extra 2500ish for a full float XD60 rear. Comparing these axles based solely on cost is an easy but bad way to compare them. If you think the UD60 is enough for you, then go for it, just know that if you do break it, it'll be an up hill battle fighting Dana/Spicer for a warranty claim. I personally know a local JK owner who experienced this with his UD60 rear axle after a ring & pinion failure.