Which Effie?

Personally I favor the +atk one. In my opinion Effie importance is Atk>HP>DEF since her big draw, especially with a brave lance, is the absurd damage. Defense CAN help her damage if you put bonfire on her, but usually she kills stuff without it anyway. Plus HP keeps her above half to keep wary fighter going for longer, at least assuming she has to eat hits from casters since she can't usually get in without support throwing her forward with reposition, or just tanking a hit and then killing in return

personally, i would merge the 5* with the 4* and get it to 40+10. that way youll have a +atk effie thats as strong as a 5* +atk effie at 40+5

The +atk IV is better with brave lance.