As a rule of thumb you could say that a plain edged blade can do the work of a serrated blade but any blade canīt do the work of the file.
I would definitly miss the file on my multitool. IMHO the file is an added utility while the serrated blade is just one more blade. So I would choose the RS only if I had a dedicated use for the serrated blade in mind (I donīt but maybe you do) otherwise Iīd go for the X.
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If it isnīt broken, it doesnīt have enough features yet.