Obviouslly excluding the Sinnoh region's honey trees, which of these two are, overall, harder to encounter (taking Pokémon XY as a reference)?
The chance of a Shiny female Combee is about 0.0000310251%. The chance of a Shiny White Flower Flabebe is about 0.0000024414%, so Shiny White Flower Flabebe is rarer.
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