Ouch! Even a quick comparison is gonna be difficult. A review of those two manufacturer's websites shows Ernie Ball markets 15 different electric string sets and D'Addario a whopping 72 sets! Or is it acoustic strings you're interested in?
Ernie Ball's site features a "Tone Universe" which might help someone weed through their offerings;
http://www.ernieball.com/tone-universe
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins