Button with Nine-patch or Style?

I'm making an app with custom buttons, but I want to know is it better to use the nine-patch tool or define styles and colors in xml. My buttons change in height and width but they do not have images, just words, something like this:

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Solution

Please check this link also. What should i use for better performance, nine-patch or drawable xml resource?. Both approaches have is own merits. Select one option as per your situation