I suspect they are both pros. I happened across JY at the public library a year or so ago when I borrowed his book Visual Tennis. It has really helped me. I've been a good player w/o fundamentals and his book has connected the dots for me and taught me fundamentals. I'm now using his strokes to teach my children the game. I don't know Oscar or have taken time to read his stuff. I've felt JY's techniques are open to cover many situations and strokes by detailing moments in the strokes where all good players are either the same or similar which makes sense to me as someone w/ a very good golfing background and having seen many, many golf swings that all work but look different.