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The classes have been around Android for so long, that a lot of people forget that it can be much easier to use to achieve your texts scheme, whether adding bold, underlines or making funky animated text just using spannables.
+Mike Wallace mentioned that
The obvious differences aren't always clear, but with spannables, you can achieve more. You'll be able to style your text even more, per character styling, style text animation and even style in places where you can't normally.