What is it like to walk on two prosthetic legs? would it be harder or easier than on your own legs?

More difficult: More difficult for several reason, primarily because you have no sensation touching the ground. This is known as proprioception and lack of it affects balance.

Harder: Walking with a prosthesis requires more energy. The amount of energy depends on the level of the amputation. For example, it is much easier to walk with a below the knee (transtibial) amputation than an above the knee (transfemoral) amputation. Walking with two prosthesis below the knee is easier than to walk with one above the knee but most people can walk after appropriate physical therapy.