Answer: BothBoth reactions involving Cu+$\ce{Cu+}$ have the lowest and highest Standard Electrode Potentialsstandard electrode potentials, respectively. Thus, Cu+$\ce{Cu+}$ has to be the strongest oxidizing/reducing agents, and therefore it undergoes disproportionation.
Because the formation of Cu$\ce{Cu}$ has a higher SEP than Cu+,$\ce{Cu+},$ it is more likely to get reduced and therefore is a better oxidizing agent — - NOTnot a better reducing agent -— than Cu+$\ce{Cu+}$ (which is more likely to get oxidized as it has a higher SEP).