Bordeaux wines are usually a blend of three or more grapes, with the predominate grape being the one most grown on that Estate or in that Appellation.
For instance Chateau Lafite Rothschild is in the Paulliac Appellation where Cabernet Sauvignon is the predominate grape and may make up as much as 95% of the wine, to as little as 70% depending on the winemakers quest for a specific taste.
More and more California vineyards are blending in other Bordeaux grapes with the Cabernet Sauvignon, including Merlot, and Cabernet Franc.
I find that generally speaking, 100% Napa Valley Cabernet Sauvignon is often more robust and sometimes more heavy in flavor than a red Bordeaux, however, the Bordeaux may have more complexity and extra nuances of taste.
Taste is what it is all about, so Enjoy - there is no Best, except in individual taste!