This is an issue that is near and dear to me. These two choices are, in my mind one of the defining aspects re; the differences in wing chun. In The Ip Man/ Hong Kong houses, this one strategy,choice...a gate, if you will, is one of the most fundamental modifications to wing chun as a whole, since it concerns the root. If the spine is the core, than this more than any other singular idea changes everything. My first wing chun style, Leung Ting emphisised this idea as the standard method to exchange energy/ deploy tools and reckon footwork.
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Mr. Wrong demoing center body (waist) turning.
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Mean while, arch rival and 100 percent waist turning (as is Wong Sheung Leung, Tsui Sheung Tin umongst others) demoing in Wing Chun Vs. Jeet Kune Do Vol. ! The failure of wing chun structure/tools using modified (read Leung Ting) shifting.
This exchange of energy in my opinion modifies all subsequent tools, structure and footwork.
This I think it is the brainchild of Master Leung Jan. I used to think it was an invention of the Red Boats and their restricted environmemt but shifting seems to have come after this period, with no wing chun from there back seeming to have this strategy.