If you're talking high level IO'ing when you mean end game then my money is on Invuln. It just has so many layered protections. With capped HP, super high S/L resist, good resist to everything else and the defense cap to all types but Psi there are few things that can kill an invuln.
Then again, WP isn't too bad either. Super high resist to S/L and I believe it's possible to hit the defense soft-cap to every damage type but Psi. Plus you get extra HP from HPT and Accolades. Not enough to cap you, but enough to make RttC an incredibly potent regen buff. On top of that, WP gets decent resist and defense to psi. Something Invuln completely lacks. You also get a self-rez and Quick Recovery.
I think invuln gets the edge because with Burnout you can run your god-mode power twice in a row for a long period of being nearly invincible. Some people like to use Dull Pain as a big heal as well. They get enough recharge to make it perma, but only use it when they are getting smacked around and need a big heal. That ensures that they have the heal when they need it, and in protracted battles it's recharging fast enough to always be on.
Either way both of those sets are at the absolute top of the survivability charts when you IO them to the gills. You really can't go wrong either way.
I know it's probably been said but I need a quick and easy explanation. My current favorite project is my SS/WP Brute who is fun to play but I keep having scruples with /WP and need some clarification. I solo more than I team and /WP has been more than helpful in the solo category but at times on SO's doesn't feel super sturdy. I know sets change everything but I'm waiting til end game to dive into that. The toon was an INV/EM Tanker from days of yore before I restarted him months ago. I liked Invuln for the simple fact it could take a face-bashing for a while before anything really happened.
Which brings to my question: In the educated majorities' opinion, which outshines the other in the end game content? /WP or /INV? With and without sets. He just hit 32 today and I have enjoyed him thus far but like I said part of me misses Invuln for some odd reason. Is this crazy? Should I just shut up and see the beauty of /WP in the last chunk of my leveling experience? Thanks in advance for any answers you Brutes you!