the efficiency of shields vs. guns is 20%. so a gun that is "strong" vs. a type of shield does 20% more damage, while a gun that is weak will do 20% less damage.
personally i d like it if it was more like 50% to have an even greater impact. gotto keep in mind that capital ship weapons, nomad weapons and codenamed do not have any type. - so they allways do 100% damage.
furthermore it would be nice if shields beyone 10k strength would still show a graphical difference. ( upon getting hit, they all show 3 hexagon shaped tiles in white... )