Neither. Trading will make this game easier than what it is, specially to get gear or the weapons you want. Equip more Exotics? No, just no. That means they have to nerf EVERYTHING in the game.

Multiple exotic slots wouldn't make sense. Bungie explicitly stated that choosing your gear wasn't supposed to be easy. There's a reason you have to go to the pause menu to manually switch gear in the field, or why you lose ammo when changing your loadout in combat. It would also reduce the significance of finding raid gear since you would just need TWO raid pieces and have the other two be exotics. PvP would also be a bigger joke than it already is if people could equip things like the Thorn + Invective, or the Suros + Pocket Infinity. It would be ridiculous. Also, there just isn't enough content in the game to allow for a trading system. There aren't many exotics and only 1 set of raid gear that takes you to the max level. Everyone will find ways to trade off the exotics/raid gear they don't need and exchange it for stuff they do need, allowing them to bypass RNG and grinding. Activision doesn't want that.

Just gimme more vault space.

Exotic system is fine. Trading would ruin the game.