There's really no way to qualify it like that. Every player is different, and different things will work for everyone. The CY is what comes with the student/lower level intermediate Yamahas, but these are machine made. Handmade CY's are each going to be slightly different, and even more difficult to categorize.

When I inquired as to how they came up with the CY cut for their 581 model pro flute, I was told that when Yamaha was doing their R&D, they actually had sixteen headjoint designs in a box. This box had been flown all over the world to professional flutists in major symphonies. The flutists were asked to vote for the cut they liked the best and the overwhelming favorite was the CY

http://www.fluteplayer.net/2006/01/yamaha-cy-headjoints.html

The article is dated and specifies the date of the CY headjoint purchase at the beginning of the article.

Bob Affifi is a professional flutist. In his article he makes no mention as to how much practice or lack there of he was making at the time of his headjoint purchase.

I can't readily google when the EC came about, but in the comments section of the above link Bob Affifi does go on to comment about the EC vs the CY, in the comments section:

The EC cut is geared more towards the bottom end, i.e., louder/stronger low notes (like the Sankyo NRS-1) whereas the CY cut is more balanced throughout. Big low notes are in vogue these days and so Yamaha is simply responding to the market by shifting to the EC. For what it's worth, I still prefer the CY.

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The preference for the CY headjoint is a personaly preference for the writer, but it was the Yamaha R&D bit about testing multiple headjoints and finding the CY a superior cut (in the 90's) that was interesting.

had a CY head that I preferred over any of the EC heads also. One EC head I tried was horrid and then another one was just okay. I am not particularly found of the EC, I can't seem to produce much color with them. They have always played too straight forward for my liking. The CY was always fuller for me and I could get better tonal dynamics on it. I suppose I have been spoiled by other handmade heads by some great makers, so that may be why I don't care much for the Yamaha heads. I just never could understand what the big hype was over the EC heads. You never hear of any professionals playing on them, so it makes you wonder...

Bob, is a very talented jazz flutist, so I highly doubt he is out of practice and is still playing strongly as far as I know. The info comes from a good source.