Keep the effect Emmisive Armour is supposed to have as well. One 40 point bLast would deal 30 points of damage aginst Emmisive Armour I but 4 10 point bLasts would be completely absorbed.
Without that, or with bugged Emmisive Armour
, I'm not sure it matters except in that, if your target is hard to hit, 4 rounds would give you 4 changes to score with 1/4 of the damage and that might just make the difference.
Note that I'm talking about shots in the same round. Stretching out the damage over several turns is a different situation!