First you need to decide what the reel will do the most ... cast or jig or equal. That will help make the decision. You are correct, on all facts. To me the choice is simple if you plan to cast with the reel buy the 10,000FA. It has both the higher drag & higher retrieve but to be honest anything over 35-40 lbs. of drag on a spinner is irrelevant because most wont hold up long.
For casting I only use the 10,000 FA, for jigging I use the SW20000PG (Japanese Model/Power gear). All our casting set-ups are the 10,000's with either the 10,000 spools or the 20,000 spools.