There is something special about a prestige cuvée that is truly a blend of 50% Chardonnay and 50% Pinot Noir. For many, it's what makes champagne, "champagne".
Don't get me wrong. I'm not saying that a 50/50 blend makes the "best" champagnes. Besides, most prestige cuvees are "close" to being a 50/50 blend so it's somewhat of a moot point.
But it is said that a perfectly even balance of CH and PN creates a unique tension in the mouth and in the wine.
I think if I was a cellar master, I would designate that my finest cuvée would always be an exact 50/50 blend each and every vintage. I think it would make the blending an interesting yet firmly stated challenge. If I had trouble doing that with a vintage champagne, then I might opt to make my prestige cuvée a blend of vintages a la Grand Siecle. I could then tinker with older vintages but always return to making sure it was precisely 50 CH and 50 PN.
Anyway, I found that only a few "big name" prestige cuvees are a perfect 50/50 blend (or so they are stated):Heidsieck & Monopole Diamant Bleu for the years of 1995, 1996, 1998
Laurent-Perrier 90/93/95 Grand Siecle
1990 Dom Perignon Rose
1996 Dom Perignon
2000 Dom Perignon
Dom Perignon seems to pride itself on being "nearly" 50/50 every year. And it is always one of the most finely balanced champagnes, in my experience. Just a coincidence?
Perrier Jouet's famous Belle Epoque bottles are also "fixed" in their nearly even percentages every year except they always include 5% Pinot Meunier in the cuvée.