Who receives precedence if both an Avel and a Yahrzeit want Maftir?^[1]

A person with a Yahrzeit that week receives precedence over an Avel within the year, even if he is within Shloshim [or on the Shloshim].

[1] As is the law regarding Kaddish and leading the prayers, in which a Yahrzeit receives precedence; Az Nidbaru 2:72 that so is the custom even though receiving Maftir for an Avel is brought in the Rama while receiving Maftir for a Yahrzeit is only a custom; Piskeiy Teshuvos 284 footnote 8

Other opinions: Some Poskim rule that an Avel within the 12 months receives precedence over a Yahrzeit regarding Maftir. [Maaseh Eliyahu 294, brought in Pnei Baruch 35 footnote 32]