Answer
Constant pressure.
Work Step by Step
For a constant-pressure process: $\Delta s=c_p\ln\left(\frac{T_2}{T_1}\right)$
For a constant-volumeprocess: $\Delta s=c_v\ln\left(\frac{T_2}{T_1}\right)$
Since $c_p\gt c_v$, the entropy change will be greater for a constant pressure process.
