I will have to take a moment to point out that it's well known that Geekbench is woefully inaccurate and is limited to testing memory (RAM and HDD/SSD) and CPU, but only in a way that reflects performance in regular consumer applications with fairly little memory being used.
GPU's do not factor in at all and because of the small amounts of data used in the CPU tests, the main feature of server and workstation CPU's, a really big Level 3 (L3) cache, doesn't get to show it's worth. Combine this with both using the same SSD and the automatic error correcting in EEC memory the Mac Pro uses leveling the playing field, it's only the natural conclusion.
RAM in general is woefully slow compared to modern CPU's and the purpose of cache is to act as a much faster place where the most commonly used parts of what's in RAM is stored. This means that on average the CPU doesn't have to wait as long for data from RAM. The applications for which workstation and server CPU's are used (like editing audio and video) generally involve working with large sets of numerical data and in those tasks CPU's like those in the Mac Pro are miles ahead of anything else.
The only reason why Geekbench is so commonly used is because it's the only well known cross platform benchmark. On the Windows side everyone uses PassMark or Futuremark benchmarks, which aren't available on OSX. Personally I'd recommend that rather than Geekbench, people should use Cinebench and Uniengine Heaven or Valley.