For PVE I can easily say with very little difficulty that I have fallen absolutely in love with the Obsidian Mind since I got it; there's little more fun than clearing an entire room and then seeing "SUPER CHARGED" pop up for your efforts. That said it sort of inspires a different play style for using Nova Bomb, rather than waiting for a tough fight or a heavy enemy and eradicating them with your nuclear light, you'll often find yourself more interested in taking out that large group of enemies you'd just as easily one shot all of in seconds with your weapon of choice. All that on top of having no real benefits for Sunsinger aside from the passive increased super energy from enemy kills and the +36 light it all boils down to preference and play style. PVP the majority of my time I ran Voidfang simply because I needed them to raise me to a level 29 at the time, and never really noticed the buff since I hardly rely on my grenades. Personally for PVP I don't feel like your exotic armor matters very much in the slightest, nor even your weapon. I've done decently as a level 1 Titan with no skills and a Khovostov so in the end "what's best" doesn't really matter, as any little boost you get is just that, a little boost. None of this applies to Iron Banner of course. Tl;dr: use what suits the way you play best. Melee a lot? Probably the Claws. Grenade a lot? Voidfang for sure. Or if you just want to vaporize every last Dreg and Thrall you see with a ball of inter-dimensional plasma, probably Obsidian Mind. It's all up to you on how you want to play the game.