Doge because it came first and is based on a popular meme. Catcoin was created to rival doge, and because of that I think many people will move away from it and stick with doge. Also becuase doge was based on a popular meme, it already had a fanbase prior to the coin coming out. This caused the quick creation and use of market and information threads on this website and many others such as reddit. On reddit, dogecoin is one of the most active and well operated altcoin markets and had numerous posts after the first day of its inception. Catcoin was released December 24th (I think), and today, the 26th, there is only 1 post on the catcoin market subreddit. That being said doge has its problems, mainly the huge premine at caused many to have a large amount of doge before it was released to the general public. So while doge will probably be the one to get to the moon, catcoin will probably still have a place in the altcoin world.