m-CPBA Selectivity between Baeyer Villiger Oxidation and Epoxidation?
The answer appears to be "it depends" (perhaps this should not surprise an experienced organic chemist). 

According to the abstract of the paper by Mendelovici and Glotter [1] in steroid chemistry:


  Treatment of 3β- and 3α-hydroxy-(acetoxy-)cholest-4-en-6-one and of 6β-and 6α-hydroxy-(acetoxy-)cholest-4-en-3-one with MCPBA gives two types of product, depending on the initial site of the peroxy acid attack. Attack at the carbonyl group gives a Baeyer–Villiger rearrangement leading first to enol lactones and then by epoxidation of the latter to epoxy lactones. Alternatively, attack at the double bond gives epoxy ketones which can subsequently undergo a Baeyer–Villiger rearrangement leading to epoxy lactones. With one exception (3α-hydroxycholest-4-en-6-one), the Baeyer–Villiger oxidation of the enone is the dominant process. Epoxidation of the double bond is suppressed in the presence of an axial 3α- or 6β-acetoxy group.


However, Kazmeier and Horn [2] working with unsaturated aldehydes find 


  Purified m CPBA is a useful reagent for the oxidation of several classes of aldehyde. Although linear unbranched aliphatic aldehydes are oxidized to the corresponding carboxylic acids, α‐branched ones undergo Baeyer–Villiger oxidation to formates. α‐Branched α,β‐unsaturated aldehydes provide enolformates and/or epoxides, which can be saponified to α‐hydroxy ketones with shortening of the carbon chain by 1 carbon. Unbranched α,β‐unsaturated aldehydes undergo an interesting Baeyer–Villiger oxidation/epoxidation/formate migration/BV oxidation cascade, which results in formyl‐protected hydrates with an overall loss of two carbon atoms.


Overall it appears that both processes can occur so Murphy's Law applies. It would be a good idea to explore alternative epoxidation conditions for an unsaturated ketone.

References


Mendelovici, M.; Glotter, E. Epoxidation and Baeyer–Villiger Oxidation of γ-Hydroxy-Αβ-Unsaturated Ketones on Exposure to m-Chloroperbenzoic Acid. J. Chem. Soc., Perkin Trans. 1 1992, No. 13, 1735–1740. DOI: 10.1039/P19920001735.
Horn, A.; Kazmaier, U. Purified MCPBA, a Useful Reagent for the Oxidation of Aldehydes. European Journal of Organic Chemistry 2018, 2018 (20–21), 2531–2536. DOI: 10.1002/ejoc.201701645.