I have a question, i got it and vow of love together, it says effect is duplicated, this one is +50% but only for lightning units, does it really nullifies vows of love +30%atk ao only my lightning ones get 50% and the different elements ones get nothing?
Aigaion, Steel-Plated Destruction VC would be the best for him in terms of damage, with 20% slash res penetration and +25 slash attack (and +25% hp). This card would be good if you had a second lightning-based phys attacker though such as 9S or Charlotte perhaps, but there is also Ifrit's VC if you specifically wanted +50% attack up for the party.
But it would most likely be worth getting if only for the esper if nothing else. The combination of +50% attack (Ifrit VC) and +20% Slash Res (Hourne's First Division <Solidus> VC) into one card is good, but this would really only benefit if you had two or 3 mono lightning team.