Small attacks does a random damage between 10% and 20% of your total SED.
I think on average small attack does 15% so 6 x small attack on average does 90% of total SED.
One big blow does 100% of your sed no random

N tickets give a small (~10%) chance of getting R or SR cards, and smaller (~5% chance) chance of randomly upgrading a R or SR card if you get a level 100 N card. From what I've seen, it's better to spend on gatcha tickets than wild cards.