There are many benefits to a fixed spindle/hub design over the sealed unit bearings, which include:
1. Super strong design
2. Reduced front driveline vibration
3. Reduced front u-joint wear
4. Ability to use 2Low
5. Increased fuel economy (not a great deal, certainly not enough to offset cost, but still an added plus)
6. Reduced front driveline wear & tear (ring & pinion gears, bearing, seals, etc. )
If you base your decision solely on potential "fuel savings", you're sure to be disappointed. Don't get me wrong, you will see a slight increase in MPG, but the "savings" will never offset the cost of the kit.
For me, I honesty could care less about the "benefits". I want this kit because I like having lock-out hubs... . period.
Ryan