Antenna efficiency tied to material?

I was wondering if the material that used for antennas on the current FRS/GMRS radios is less conductive and causes more loss of transmit
I had looked at some old talkabout 250 antennas and they were copper,
which is one of the best conductors.
They got out great for a 1/2 watt set.
But looking at todays current sets , I notice that they appear to be made of steel or some other stiff , springy material.
Could this be a signifficant source of the mysterious power loss at the antenna that most new sets seem to have?
At 5 watts in and an average of 1 to 1 1/2 watts out , where does the power go with the newer breed of bubble pack type sets?
Is this bad for the radios and shorten their lifespan?
Maybe someone more knowledgable than myself can help answer these questions for me?