Originally Posted by
acideraser
I just don’t want a new crank less stiff than messenger as I assume it will affect the power.
Quite honestly, I really don't think you'd tell the difference. Not trying to be rude but unless you're huge, strong and racing track sprints one crank will feel much like another. Even then, the sprinters I know couldn't care less what their cranks are.
If you want ultimate stiffness it's Omniums (discontinued), Dura Ace 7710 or Sugino 75 but most people (myself included) buy what they like not what they need.
Originally Posted by
acideraser
also are GXP or hollowtech II systems better than JIS sq. taper for fixed gear bikes?
Plenty of Keirin racers still using square taper as well as countless thousands of happy fixed gear riders. I don't think anyone could honestly justify why one might be 'better' than another in the real world so again, just buy what you like.
I have 7710 on my commuter and Sugino 75dd2 on my main bikes. Personally I prefer the Sugino as they copied the hollowtech II system so bottom brackets are far more readily available but can I 'feel' a difference? Hell no!
With reference to the models you mentioned and compatibility with your chainrings; some of the basic Miche cranks are well known to be more prone to failure than others; however, I would say as long as you steer clear of really basic unbranded chinese imports just take your pick for whatever suits.