RoA VS Morello

After read a post this post Kassadin EXPLAINED IN-DEPTH (Kassadin Main #1 NA) I Have my doubts about RoA on Kassadin

The biggest and most debatable question everyone and there mother is going to ask is "Why don't you build Rod of Ages?" Don't get me wrong it's not a bad item for him but I believe that Morellonomicon is a better and more cost-efficient replacement while keeping all the other items in its place. With Kassadin you play as a glass-canon, no need for extra health, just need raw power.

Let's talk about Rod of Ages: Gives +300 Health and Mana and +60 Ability Power maxing out to +500 Health, +400 Mana, and +100 AP. It's passive is 15% damage taken is gained as mana and spending mana restores 20% of the cost as health up to 25 per spell cast. The amount given overall is "good" but that's all it is, just "good", not AMAZING or EXTRAORDINARY. You won't be utilizing its passive to its fullest since you will be playing in the shadows and looking for picks most of the time.

Now for Morellonomicon: Such a cost-efficient buy with everything needed on a mage especially Kassadin since he's an insta-burst assassin. The recipes to build up are too good to pass by, Lost Chapter giving you mana back, Fiendish Codex with it's 10% CDR, both giving a good amount of AP, and even though it costs +200 more compared to the Rod of Ages, the build up to it is cost-efficient. The item itself gives you +20% CDR, a flat +400 Mana and +100 AP (Rod of Ages Mana and AP stack maxed out) unfortunately no health, but that's a small price to pay for something that benefits you throughout the game. Going to one of its major functions as an item is the passive that restores +20% of your maximum mana on kills/assists. This is a game changer in team fights. Most of the time you'll be using your Riftwalk aggressively and in no time you'll hit 4 stacks which is the danger zone but also your greatest strength. With a constant rush of assists/kills you'll decimate the enemy with the the mana restoration you're getting and lets not forget the Grievous Wounds passive to prevent healing; Rod of Ages can't give you this blessing.

Kassadin will not exploit the full potential of Roa's passive, Eternity, since he is a assassin and as such is not designed to receive large amounts of damage and survive. Roa only restores 25 points of Health as maximum per cast. On the other hand Morello facilitates and rewards the kills I think the Roa's passive, Eternity, is best on frontlaners like Swain or mid-range mages like Ryze Since both can withstand the damage (with Healing or Shields) and require large amounts of mana

Comparative Table

which do you think is the best option as a First full Item?