The marginal benefit of +2 Black basic defenses to +1 Purple active defenses seems interesting, but it doesn't seem like an obviously worthwhile choice compared to spending an Action advance to get a whole new action to add to your arsenal. Do folks find the Improved active defenses to be worth an advance?
+ 2 Black (average 0.67 Challenges generated)
+ 1 Purple (average 0.75 Challenges generated)
So a slight (0.09) increase in Challenges generated against your attacker, and more chance of the attack Banes and Chaos stars, but is it worth it?