If using the mixture simply as an extraction solvent, you should notice no difference between xylene and ethylbenzene. As meth freebase is miscible with methylbenzene* (better known as toluene) then it's likely miscible with both ethylbenzene and xylene, as well as any mixture of the two.
If your mixture isn't clear and colourless you should distill it. Otherwise it should be fine.
* Ref: Post 503524 (https://www.thevespiary.org/talk/index.php?topic=8217.msg50352400#msg50352400)
(Osmium: "To answer the question, toluene and meth ...", Stimulants)