As you can see by title i can't decide who to take 
or 
i just can't decide, but im for sure i wanna take atleast one them....
I hope someone can help me, and btw i can go where ever i need like i know Draven is adc but still if i buy then i will play adc but if i buy Rengar then i can go jungle or top and try one of all buils cause all i know you can try lot of build for him and if im right i think Rengar will have the rework out soon but still im not sure...
The champions are complete opposites. One is a carry and the other is a carry killer. I can tell you rengar is getting a rework that will be out in a few weeks. Draven is difficult and is also rather weak right now even when played well.
I can post a couple of videos so you can see what you like though. (im not sure if you are new to the game or not, sorry if that is not the case)
https://www.youtube.com/watch?v=4hmeNnIUY6M
This is a video showing why people play rengar
https://www.youtube.com/watch?v=XDXz2jEwniQ
here is a video with draven being played by high level players
rengod is getting reworked just saying
