re: Any guitar players on this board? (String preference)

EXP is a D'Addario proprietary string-life-extending coating, "80/20" is a broad industry term describing a specific bronze alloy - specifically the mix of copper, tin, zinc. 80/20 is a term used by multiple manufacturers. "Phosphor Bronze" is a different specific bronze alloy used by multiple manufacturers.

Easiest loose description I can give you ... the 80/20 alloy generally (VERY generally) is said to be tonally brighter, the phosphor bronze tonally warmer. But some people's will tell you just the opposite. Why? It's a case by case, taste by taste personal perception thing, not a right vs. wrong thing.

Try both and lean towards your preference. I prefer phosphor bronzes and it's what I put on most guitars I work on. But I stock both alloys.