englishal, easier or harder than what? Do you mean is it easier to land a twin TD than a single TD?.. or harder? If that is your question, I can say it depends on the plane, but generally, a twin has more mass and is less likely to be squirreled about by cross-winds, however, a strong steady cross-wind has more push on the larger rudder area, and requires much more aggressive rudder inputs, including muscle strength. My first flights in a DC-3 had my legs literally trembling from hard thigh-muscle exercise.
But more to the point of conversation on this thread, gyroscopic precession does have a measureable affect on landing.
A single-engine, when rotating the pitch for the flare, in very calm air, will yaw to the right during the flare. A twin with counter-rotating props will not yaw. A twin with both props rotating clockwise will yaw right during the flare, but not as much, it seems, maybe because of mass of weight, but it is there.
However, I don't think that there would be very much yaw on the ground after touch-down to cause a nose-over. All of these things mentioned lend to the tendency to nose-over. Also, is the basic fact that there isn't a nosewheel to prevent the occurance when to much brake is applied to stop groundlooping, which is the primary cause, ...I think.