Does anyone know how much if a difference there is between these two?
There is a heap of difference the HD is much thicker and resists running off a vertical surface. I use it on the boat trailer and springs it will last 12 months with many trips to the beach. Once it has flashed off it will remain just tacky not quite dry. Okuma use it inside their Game reels to repel water.
So i take that it would work good on reels i service for myself and for others.
Please read Alans extensive thread on lubricants for the most suitable products. Its the first thread on the home page under "tools and lubricants'