Among the official releases (I'm not conversant in all the bootlegs and YouTube versions), the correct answer is Beast Over Hammersmith. That version was recorded before the studio version was even released, and it is played at the proper tempo. Later live versions are sped up significantly, some to a ridiculous pace. Give Clive Burr credit for keeping the band on track better than Nicko typically does on this song. Steve's bass on this mix sounds awesome, too.
I also love the Live at Abbey Road performance. For those who don't know it, in 2006 the band performed "Hallowed Be Thy Name" and "Brighter Than A Thousand Suns" start-to-finish together in studio (no crowd) for television broadcast. Both performances are electrifying, and make one wonder why the boys don't do a "live in studio" album, which I'd buy immediately. I don't know if there is a high-quality audio recording available, but it no doubt can be found on YouTube. It may still be broadcast from time to time (the episode also had live performances by Natasha Bedingfield and the Gipsy Kings, which is a pretty weird combination). It has earned "never delete" status on my DVR.