The wire line was very easy to handle
why would a rubber coating change the characteristics of the way the wire acted ?
if it rusted, i could see your point.
but the rubber would not change how the wire would spool on your reel.
what the rubber coating will do is
INCREASE the diameter of the wire,
so you will have to put out more rubber coated wire to reach the same depth that regular wire would.
also the rubber coating will probably not be as slick as the wire itself, which will cause more drag and once again increase the amount of wire in the water needed.
like other have suggested maybe it was leadcore.
if you really dont like wire, try monel or the leadcore, i would try the leadcore first, "easiest" and most forgiving of the 3 to work with.