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Synta or Guan Sheng, optically there is not much difference. Both fall into the category of delivering images to the eye which have a wavefront that does not give blurry images. Wavefront error for both is less than 1/8th of a wave of sodium light (seen them as good as 1/10th) that's after primary and secondary reflection. Test done using Foucault and Ronchi tests, as well as comparison of stars as per "Star Testing Astronomical Telescopes" by **** Suiter. (Also see ATM Journal article on what the eye can see with verious wavefront errors.)
The difference lies in the side bearings. Synta with the handles and Guan Sheng with the springs.
Both have their disadvantages.
The GS Spring was a *******isation of an invention that appeared in the Amateur Telescope Makers Journal or Magazine, about controlling the balance of a Dob with tangential pressure on the altitude bearing by using a spring. The GS one is nothing like that which was proposed! It does work in a fashion, but not as per the intention of the original designer. A tangential control gives EVEN control over the entire 90° of travel in altitude.
The handles on the Synta have their problems too. There is a small ball bearing thrust washer on the handle closest to the observer that bears against another threaded washer onto the side of the rocker box. Through overtightening or constant adjustment (even disassembling and reassembling) the threaded washer can lose its thread and fall off, leaving you with a hand full of ball bearings (fixed a couple now). The tension from this handle can also distort the rocker box side, giving a non-orthogonal bearing. Not so good for DSC's.
So take your pick, one is just as bad as the other.
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