The rubber stuff will outlast the other stuff unless painted with a UV
inhibitating paint. However the rubber sometimes usees amonia af a
blowing agent to make the rubber foam up. This amonia will react with
the copper and make it brittle over time.

If rou the pipe is somewhere where it will be constantly wet, use the
plastic foam.

There have been studies done on this. The effect is called "Stress
Crack Corrosion" and can cause refrigerant leaks, especially in under
ground lines. (Don't run lines underground for many reasons, this is
just one of them).

The reason you insulate the lines, besides reducing the chance oc
condensation damaging something, is to keep the refrigerant as cold as
possible. The refrigerant cools the compressor motor better if it is
cold, prolonging motor life. It also keeps the refrigerant hot gas
discharge temperature lower, which is better for the refrigerant oil,
as hagh temperatures can break the oil down. The compressor is a gas
pump. It pumps just so many CFM at any given pressure difference. If
the gas is colder, more mass is pumped, increasing efficiency.
So insulate those lines and keep that gas cold.

And if the lines are outside, the insulation will last longer if you
wse a UV retarding paint to coat the insulation.

All that said, I usually use the rubber as the best insulation for most
of my applications.

Stretch