Ok whats you thoughts on this is there any advantage or disadvantage.

It would depend on what pressures you were likely to be running..
how anal you are about weight and possibly what happens to be in stock in your local shop.
Currently my rims have fibre glass tape in them which withstands pressure no problem, but, it's a bugger to remove.

Currently I use black electrical tape.

Velox everytime

Plastic lighter then ? i have had caces of rotting velox in the past wet winters so plastic it is

I have been using velox but last year had a flat that was due to the velox rotting through and giving way at the spoke hole. I have been wondering since if its worth changing to something else, but I figure the rubber types will also give up the ghost. Anyone used plastic and does it slip?

I prefer Velox but you need to change it once in a while, well on my road bike that is.
I prefer the plastic stuff on the MTB as it can be wiped down to remove grit and thorns etc.

Currently I use black electrical tape.

+1. Cheap, strong and flexible. I use 2 layers, and never had any problems.

I once used electrical tape and the adhesive melted the tubes?

You had it on the wrong way round. Sticky side goes on the rim. 😉