the only matte finish i would buy is black, it gets dirty easy.
So get matte if a dark color - gloss finish if its a light color
I just got the Elago S4 slim case or whatever it's called in matte grey off Amazon for $10. It's pretty nice. They have most of the colors with the matte feel. I just wouldn't get the white one because it gets dirty. The grey looks good on the white iPhone.