The obvious and critical distinction between electron and proton transfer is the almost 2000-fold difference in the mass of the particle.
The tiny mass of the electron allows transfer by quantum mechanical tunneling to proceed with modest driving forces at a biologically meaningful rate over distances of up to 15 Å, and non-physiologically beyond 25 Å. At these and even much shorter distances, the donor-acceptor interaction is very weak and the electron transfer is clearly in the non-adiabatic regime.
