Well from what I read on Warn website, not much. From website:
WARN Standard Hubs are the ideal choice for OEM hub replacement. These are the same basic hubs Warn Industries has supplied to OEMs around the world. WARN standard hubs share many features with our premium hubs such as a 4140 steel clutch ring and inner drive gear and a precision cast hub body.
The WARN Premium Hub is a no-compromise hub designed for the hardcore off-roader or truck owner who will accept nothing less than the industry standard in performance.
The all metal construction and ZA Alloy dial ensure years of reliable functioning. This dial requires a full 9/10ths of a turn to ensure positive engagement of the inner drive gear to the clutch ring. To make sure they stay engaged, WARN premium hubs use a thick internal wave spring and heavy dial detents.
All WARN Premium Hubs feature:
- 9/10 turn dial for robust engagement/disengagement
- Heavy detents for positive engagement
- Wave spring technology increases reliability over standard coil springs.
- All metal construction
- ZA Alloy dial with dual seals keep contaminants out
From what I see, difference is the look and apparently heavier innerds, as well as 9/10 turn dial