It’s the one you like the most!
Chardonnay vs. Pinot Noir vs. blends - Chardonnay and Pinot are the most widely planted grapes in the region and most Champagne is mostly a blend of these + or - Pinot Meunier. Straight Chardonnay and straight Pinot Noir Champagnes are also common.
Chardonnay Champagnes tend to be lively and mineral and can offer aromas and flavours of white flowers, citrus, grapefruit, chalk, green apple. Aniseed ginger and bread. If they are ages long on lees in bottles brioche, almond, stewed fruits, toast, grilled nuts, mushroom and more may emerge.
Pinot Noir Champagnes tend to offer body and structure with aromas and flavours including red apple, cherries, strawberry, damson plum, blackberry, cinnamon, rose and violet. As these wines age on lees, mango, fig, other red and black berries, hazelnuts, date (the palm kind!) tobacco, coffee and cacao may emerge.
Some drinkers prefer straight Chardonnay, some Pinot, some a combination of the two. The best way to unlock this mystery is to try for yourself!
Grand and Premier Cru vineyards vs. the rest - There are several hundred distinct villages in Champagne and all are capable of producing excellent Champagne. Only 17 of these are rated Grand Cru (best) and just over 40 Premier Cru (bloody good). This doesn't mean that all Grand and Premier Cru Champagnes are exceptional, nor that regular village bubbles are all meh. This categorisation came about in the 1920s when the large producers proposed paying for grapes by quality, rather than just volume. The means of ‘measuring’ quality was to determine which sub regions were the best (Grand Cru) and which were second tier (Premier Cru). That said, on average Grand Cru is best, Premier Cru next best. Some producers though will blend across 2 or 3 of these subsets if it produces a better wine. Pierre Gimmonet for instance will blend to make a better wine and in so doing loses the commercial advantage that being able to include the term Grand Cru on his label would afford. Krug also produces strictly according to quality. Champagne Bouche is another. Their 2008 is an exceptional blend of Grand and Premier Cru fruit.