A mixture of both, Probs sway towards pve though.
My advice, especially with the inception of the Prison of Elders, is that you focus on acquiring:
* Primary weapon in each burn type (of your preference: Hand cannon, A/R, etc)
* Shotgun in each burn type
* Sniper in each burn type
* HMG in each burn type
* Launcher in each burn type
I personally only play around with fusion rifles, scout rifles and pulse rifles during menial tasks like Patrols or Bounties, but when the shit gets thick and TTK (Time to Kill) becomes important, you want to know you have solid loadouts in every burn type.
Plus it is nice to have versatility in your loadouts. Any elemental shotgun will take down the same elemental sheild quickly in the PoE or anywhere else, leaving the enemy open to heavy attacks with a launcher or HMG, or headshots with your primary, etc. If for example you are fighting the Hive in the PoE and it is arc burn, you still may want to consider running a Solar Shotgun, because those wizards' sheilds are tough-as-nails solar, and your Arc damage weapons will take too long to drop the sheild, leaving you open to a quick death.
Like, when we run the PoE and we have to fight Valus Trau'ug (He recalibrates his sheild to a random burn type every time you take it down), I will typically run Void primary and heavy, with a Solar shotgun to address the Solar shield enemies.
My clanmate will run opposites, so one guy is primarly Solar with an Arc Shotty, and one guy is primarily Arc with a Void shotty.
This way, wahtever shield he pops, we have a guy on teh team who can take it down and we lay the boots to him.
Sorry if this post is too long guys. I just really love this game and love talking about it.