I use HDMI for my cable box, and if I were you, I would opt for the HDMI switcher as opposed to using component. But that is just me.
You could, however, be perfectly happy with using component for cable, as that is what many people do, and you may not even notice any difference between the two, depending on the quality of the component cables that you are using, and how discerning a viewer you are. There is no content on cable that is broadcast in 1080p either, only 720p and 1080i, and cable streams are not great sources to begin with so it is not the end of the world if you used component on it.
If you do decide to go the switcher route, check out monoprice.com for their HDMI switchers. They are much cheaper than other similarly featured models and CNET gave them good reviews, especially considering how cheap they are. i would also recommend getting your HDMI cables from them as well. Of course, even though monoprice has very cheap yet very high quality products, it would be cheaper still to just get a component cable, as opposed to getting a switcher and an HDMI cable. Just something to keep in mind.
Again, if I were you, I would go the switcher route, just because the slight quality upgrade and ease of use of HDMI (one cable as opposed to 3 video, and either 2 analog audio, or 1 digital audio cables), makes it worth it to me. And the extra money isn't an issue.
You need to decide for yourself if it is worth it to you, or if you will be satisfied, like most, with using component on your cable box.
One more thing to consider. Some cable boxes can act wonky when using HDMI. Some people see issues ranging from nonadjustable aspect ratios, to audio issues, to always having to turn on or off equipment in a certain order because the hand shaking between the components is not happening properly so they start with a black screen
These issues are more common place with older boxes or those that have not been updated. I have never had any of these issues with my box (Scientific Atlanta HD 8300 (?) DVR from Time Warner), and you will most likely not see these issues, but I would be remiss if I didn't give you all the info so that you could make the right decision for you.