I really don't want to choose because, in my opinion, they both are perfect for their role. Tange Sakura is perfect for our genki Kinomoto Sakura, and I couldn't see any other actor playing her part; especially considering that I watched Cardcaptors (shudders) I don't want anybody else playing our sweet kawaii Sakura.
However, I also love Makino Yui. She has such a gentle voice and it is perfect for Sakura-hime. She gives the impression that Sakura-hime is gentle and kind, but if I really had to choose, I would choose Tange Sakura. Card Captor Sakura will always be my first love from Japan; especially considering that it was the first anime I watched in its original Japanese and I want to keep it that way!