I going to make a confession, I do not like Champagne. It tastes awful to me. I'd rather have sparkling wine (I like Gloria Ferrar) or Prosecco. I'm a Philistine, what can I say?
But I will say this, there's very little difference between the Kirkland Champagne and the De Margerie. They are both very dry and have a not-so-pleasant sour after-note. There's not much flavor. The Kirkland is drier but the De Margerie was more bubbly.
If I had to buy Champagne, I'd go with Kirkland, De Margerie gets wonderful reviews but Kirkland is half the price.