Both. Because the entire point of exotics is that only one of each can be equipped. And its to encourage planning your build. My build is based on my exotics to create synergy if I could throw on all the exotics there be no reason to strategise and no uniqueness

Well in fact of being unique wear only one exotic you're wrong: in fact you have the other pieces that are or raid or iron banner loot

What? That Made no sense to me. But... For example if I could use exotic in every slot people would only ever use an exotic in every slot there would be no point to legendaries. And to add to that you clearly don't see how over powered that would be. If I had all the exotic armor perks pve and raiding and nightfalls would be such a joke a monkey could do it. Back to uniqueness though. Having to make choices such as using an exotic primary vs a secondary creates a chance for players to be different. I mostly use an exotic secondary but in PvP I sometimes swap on an exotic primary and I have to switch my secondary out. It forces me to really think about my build and what I am using. Some exotics compliment certain things extremely well. If I had last stand, or surous, equipped with ice breaker and ghallahorn I'd be running over atheon like he was gum on the pavement.

Ok i see your point of view and I agree on some. But remember that I said to equip even the "red" armour so we have one exotic one red and two legendaries

Probably both.