Apart from their rated power output of 750 and 850W, it would appear that both units bear near-identical specifications. Guaranteed to sustain their full rated wattage at an ambient temperature of 50°C, each pack up to 62A on a single +12V rail. As noted, they’re up to 90% energy efficient under real-world load and are multi-GPU ready, host 105°C solid state capacitors, have an active PFC of .99 and comply with ATX12V 2.3 as well as EPS12V 2.91 standards.
The 750W version of the PSU can be found online for about $170, and the 850W adaptation can be had for around $200. It is worth noting that the HX850W was recently stamped with HardOCP’s Editor’s Choice Gold Award among well-received recognition elsewhere.