I don't know why this had downvotes.
Vlad is MUCH easier to play with. He has no resources, so he can stay in lane as long as he wants. His W and E cost health, but one you only use as an escape (don't ever use it chase someone unless it's a guaranteed kill, aka no flash) and the other is for clearing waves after level 10. He gets tankier as he builds stronger and he has potential to do a lot of damage in a fight because everything he does will proc his spell vamp. But getting kills with him is reliant on enemies underestimating his damage, he can't stick to a person.
Swain on the other hand I prefer. Yes he has mana issues the whole game (please..don't ever buy tear on him...he does not work) but it's because he's crazy powerful. He has a slow and a root, both last several seconds. Her E is basically a selfish Vladimir Ultimate in that it powers up all of his damage on that target. Honestly Swain has more damage and more sustain, but because of mana he can run out and be stuck doing nothing in a fight. His last hitting is hard as well.