I think Steve76 has summed it up for those of you who are currently sitting on the fence.
Just adding to the above, in my experience, it's actually harder to find a good co-pilot position in the industry than it is to get a command job flying a single.
By that I mean a position that will give you maximum (quality) exposure in twins in the least amount of time.
In hindsight, if I was starting from scratch and had to choose between a cp or a command slot on a single, I'd go cp.
Fortunately, I never did have that option because at the time, I most likely would have choosen to log command instead.
As a result, I managed to walk out with a total of 1450 hrs of twin time in 24 months..and one way or the other the command time still came.
Now, if you are in a position where you already have the command time (and are obviously inclined to go twin/IFR) then in my opinion the decision is all that more easier.