I really like the split screen on my C330f. It is a little difficult to use with the longer lenses though - you really have to look perfectly square-on to the split image otherwise one half will go black. But its benefits outweigh that to me. It makes it easier to see when a scene is in focus, especially in dimmer ambient light.
I've used the matte screen for about 30 years. always worked perfect for me, most of the time I did use it with the help of the built-in foldable magnifier though. just tried the split screen once but it didn't convince me at all. not only it didn't work with the longer lenses, I had difficulties with low light as well.
There are two split image screens. The 4 degree prism is the most general purpose (No. 2 for the C330/f, B for the C330s), while the 6 degree one is optimized for shorter lenses (No. 3 for the C330/f, or B2 for the C330s).
Most 35mm cameras with interchangeable screens did the same thing. The prism is sensitive to the divergence of the image light, and they usually fail around f5.6 as well. Microprisms are less sensitive to angular effect but also fail when the aperture drops.