As for powder or liquid usually people use powder for oily skin and liquid for dry skin. But its also personal preference. Since you have combination skin its hard to tell which you will like better so i think you should get both and see which you like better.
Also if you do try both and end up not liking one or both you can give it to a friend who's a similar shade so they can try it.
Well good luck and i hope this helped:)

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