Yasuo Or Zed ?

Been maining Zed since he got released. He was a hella jungler cause his W cooldown could be restored by using E on monsters. He was strong and still is in good hands as I rarely have negative score and usually top damage in team with him, but there are so much better and easier picks now.

Yasuo is great as he is brokenly mobile in minions, extreme damage, overpowered windwall and quite easy to play him decently. I don't want to trigger those yas-onetrikz here, but even a decent player can make the most of that champ.
Zed on the other hand has energy, which means you MUST hit your abilities in order to have energy to fight prolong fights. If you miss or overuse everything, tour laner can punish easily and you will remain ineffective in teamfights without your cooldowns or energy. Zed can annihilate one champion, two max if fed, and he is out. Just because he must wait for cooldowns and energy. He is squishy, good cc will kill him and isn't for long fights. He is the definition of assassins, one kill and go back to reposition, wait for cooldowns and go in again. The problem is that this game has champions that are made to fight long fights like Jax, Irelia, Katarina, Vayne, Vi, Xin (mainly bruisers, the champs rito wants you to play), that will survive your burst and kill you while you have nothing.

This is my point of view and my opinion.

tl;dr - Zed is a bit harder cause you must play him more tactically and smarter, but if he is snowballing and ahead can kill anyone 1v1, until late game, where he falls off. Great laning phase, safe cause of his R and W shadow during laning and really stylish if you learn him well. Also, FARM WITH ZED.
Yasuo exceeds late game, can fight anyone in minions, falls of if he cant use his E or wastes his W. Great synergy with other champs and items, can be built tanky and still dish out a lot of damage and all in all really good champ and will pay off if you learn him.