The biggest difference is the price $558 vs $790
First, the STD (standard duty) a-arms, were designed for the weekend warrior, the person who worked hard all week and wants to play hard on the weekends with the Toyota.
The HD (heavy duty) a-arms are for more extreme offroad abuse like offroad racing, extreme rock crawling, and jumping dunes.
- a big difference is a price of $508 vs $773, plus shipping
- the geometry is the same, they are welded on the same jigs
The JBA UCAs will give you 1" extra down travel on the front suspension with more ball joint travel and more a-arm to strut spring clearance.
Standard UCAs
HD 7.5 UCA side by side 7.0 UCA