Man that is a tough question. 6X9's will give you more bass then the 6 1/2 speakers. The 6 1/2 speakers will give you more clarity then the 6X9's. There is no reason that you can not mix and match the two. My most popular set up that I do is a pair of Babb 6X9's under the back seat with two subs, and a pair of component 6 1/2 speakers. It sounds great.