I presently have a Shimano-Nexus 3 speed interplanetary hub with jackshaft assembly. I have been doing alot of performance mods and my motor just wore the hub out! I'm either gonna upgrade to a Shimano-Nexus 7 speed Hub or Sturmy Archer 5 speed. I would love a SRAM or Nuvinci but they are a lil expensive for me at this time. Whch is more durable the Shimano or the Sturmy?