Nexus6 or Galaxy S6?

Hi,

I am in trouble from a lot of days in deciding which one to buy - 

The nexus 6 or The Galaxy s6

I've read a lot about both of these but still i could not make out I hope you guys might give me a better advice. 

Also, let me tell you what all i need in a phone

-Perfect specifications for heavy games,applications

-I need a good ram management so that i can do multi-tasking properly

-Also the UI should be quite simple and sober.

I hope you guys can give me a good advice and get me out of this HUGE trouble

PLEASE COMMENT OR POLL - HELP ME PLEASE