Codeman,
"electrical grade" is probably a funny term, as all micarta was designed for, originally to be insulators in electrical systems, or something like that. So, all micarta is "electrical grade".
The difference between canvas and linen micarta is the material that makes it up. Micarta is just layers of base material and resin. material,resin,material,resin,material,etc. Add heat and pressure and BAM! You get micarta! Awesome stuff. Anyways, linen micarta uses one type of cloth (if I remember correctly, it ISN'T linen though), while canvas micarta uses canvas for the base material. There is also paper micarta, wood micarta (rare), rag micarta (holy grail of micartas, superrare!). The nature of the material used will determine its properties. SO, paper micarta gets a smooth, even, deep color and finish. White paper micarta can be scrimmed (scrimshaw). Black paper micarta looks like horn! The linens are a nice inbetween, as they look smooth and rich but the layering is still quite evident. Canvas micarta really shows its grain, and you can feel it too. The graininess of canvas micarta aids in its increased gripability.