HZ are D9, they also (supposedly) overclock better. they have better heat spreaders. they are black lol. the HK have tighter timings, though.
but i have reaf that the HK will do over 1000mhz at their stock timings if you juice em a bit....so i dunno. thats a pretty massive overclock for having those kinds of timings.
i think they raised the prices because the supply is down. when they get back up to stock the prices will come down i reckon. i will be watching for sure. now i'm thinking of buying the HK before they go up 50 bucks....crap.
they don't even usually need more volts. I've done DDR1000 on mine at 2.1v and 4-4-4-12. I bought mine "B-Grade" from OcUK for half their usual price. It just means that someone has returned them becuase they are unwanted/accidental order etc.