Out here where it is a little warm and we don't have to worry about that white stuff in the winter they only make it hard to check the compressor and keep the compressor very warm in the summer. As for noise? I think they help a little.
My two cents,
What is snow? Is it that white stuff in a freezer?
They help somewhat with the noise, and since the suction gas is what cools the compressor, heat is not an issue, the best ones Ive seen are the insulated metal box type, very quiet, Ive found a few older Bryant units where the blanket retained moisture and the compressor shell rusted through