Question

An electron and a proton possess same kinetic energy. Then =

Answer 1

The DeBroglie wavelength at non-relativistic velocities is

using

Since , for the same kinetic energy  the DeBroglie wavelength for the proton is much smaller (by the factor ) than that of the electron.

So to answer your question: the electron has the larger DeBroglie wavelength. This qualitative answer does not change if you consider relativistic velocities.