Competent Talon and Zed players farm with auto attacks and save their abilities for possible poke. As for safety, what does safety have to do with who is the better Assassin? If safety is what defines an Assassin, then Xerath and Varus are amazing Assassins. No, what matters is Assassination potential. Talon has faster damage, more reliable damage and better AoE damage. Zed is weaker in all those 3 things, but he has more safety than Talon. Is that safety that effective? It used to be pretty good, but they nerfed his W speed and put a 1 sec delay on R swap, the current "safety" Zed has, doesn't matter much. I'd rather get 1-2 kills when I engage with Talon and actually Assassinate my kill target and add some AoE damage to other targets and let my team clean up, even if I die in the process, instead of going in with Zed, failing to assassinate anything and swapping out with R saying "well atleast I got away!". Now, both champions can Assassinate effectively when FED, but in normal circumstances, Talon has stronger Assassination potential.
Zed was the overal stronger champion, because he had more versatility than Talon. His previous safety, before the W speed and R swap delay nerfs, was good and paired with his splitpushing ability before they nerfed his Attack Speed, made him stronger. But now? He can't team fight and he can't splitpush effectively.
Talon can team fight better, assassinate better and his splitpushing is some what equal to that of zed (better damage and faster turret destroying than zed, but can't escape like Zed if collapsed on).
If they give back Zed his attack speed and his instant R swap, I will agree that Zed is the stronger champion and that his less effective Assassination potential is outshined by the other bonuses he has. But that is not the case currently, so Talon is the better Assassin.