Kha'Zix / Elise

I don't know, they're both really buggy.

You probably would want to go with Elise. She is for the moment, getting more attention, and just recently had her stun majorly buffed.

Elise is more reliable, Kha might be able to snowball harder though.

Later in the game, Elise would probably be better with a hypercarry because she brings good/high damage with acceptable CC, whereas Kha brings high damage and a slow. If you're lacking in AD damage Kha might be better though.

both (im lv 5 mastery on both :D)