Both have pros and cons, but you'll find that most will suggest you get your snake on Norway rats.
ASFs take a long time to reach their adult size and will never be too large for an adult ball python. To keep a snake satisfied, you will have to feed multiples. My live eaters all eat ASFs, and have no issue switching back and forth to mice.
Norways CAN get too large for a ball python, so unless you're producing just enough to feed your snakes, you might have to euthanize some. What's nice is that you can feed one appropriately sized rat instead of multiple ASFs.
I don't feed multiples. I feed one ASF weekly. The ASF is at least 3 months old.
---------------------------------- BP owner since Oct 2008, so yeah, I'm no expert.
0.1.0 pastel bp
1.0.0 spider bp
0.1.0 albino bp
1.0.0 bumblebee bp
1.0.0 yellowbelly bp
0.0.1 normal bp
1.0.0 normal western hognose
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, chocolate in one hand, body thoroughly used up, totally worn out and screaming "WOO HOO what a ride!"