The two expressions are used very similarly. When used to describe importamt scientific research, they can be nearly identical. But both are figural expressions, and their respective figures often color their meaning. Groundbreaking refers to the initial digging of the earth for the foundations of a building. You have prepared the ground for some great construction or endeavor. Path-breaking is creating a path through great effort. Walk some distance through deep, fresh snow or drive a ship through frozen waters, and maybe you have broken a path for others to follow.

Hi Niwantha, ground breaking is more significant and more commonly used. I've often heard the phrase "this movie is groundbreaking" but I've never heard the phrase "this movie is path-breaking". If you are looking for more of an equivalent to "groundbreaking", this would be trail blazing. So, "this movie is trail blazing".