Which school is better for getting a Ph.D. degree?
Take a look at the faculty research interests and what research projects in CS are happening at each school. Of course, funding is also important.
I would add track record for job placement into the type of position you want after completing your degree (teaching? high-tech industry? military applications? other industrial applications?) to the suggestions from ucbalumnus.
You also might want to ask this question in the Graduate School Forum. You can find that by going to the main page where all of the forums are listed, then scrolling down. Here is a direct link: http://talk.collegeconfidential.com/graduate-school/
You need to do your research. I’d try to find out things like: Where do graduates of both schools go? What courses are offered at both schools? What research is being done at both schools?
Also consider questions such as : What is the cost of each school? Where do you prefer to live for the next 4 or so years?
At the PhD level, the only real thing of importance is the faculty adviser(s) in your area of research. If she/he is among the very best in the field, and of compatible personality/advising style to your preference, everything else is no biggie.
^mmm…the advisor is really important, but there are other things like fit with the department, placement rate, funding, resources, and other faculty that are important to. After all, you do have to spend most days of the next 5-6 years there, and there will be at least 4 other faculty members on your doctoral committee.