IMO like pjz99 said, a true test of rendering speed should include something like a room with several basic objects in a cluster, all with AO, raytracing and using IBL, with production quality render settings.
most machines fly through simple renders, and a 1-2 minute difference is not as significant here. if so much time is being wasted just loading textures, simple factors like drive read speed or fragmentation could have more significant an impact on the render than the actual processing power.

with a hefty scene youll start seeing overheating, pagefile usage, out of memory errors, etc. this would be, IMO, a better indicator for people deciding on what computer to buy. judging by the machines and rendertimes i could probably render this scene on a 500mhz P3. you need a scene that brings more performance factors into play.