i think it comes down to preference. if the DW threads have shown anything so far, it's that there is a path to DW tanking that is every bit as viable as 2h tanking. you sacrifice avoidance to stack expertise, but expertise offers mitigation -and- threat by reducing parry/dodge and consequently parry-hasted attacks. so on a point-for-point basis, the advantage goes to expertise, since it increases both threat and mitigation.
The point I'm holding to at the moment is, dual wielding will not result in horrible death and drastically increased damage taken, but at the same time, I haven't seen a smart spec/gear set up that makes dual wielding offer something particularly valuable that you can't get with a 2-hander.