From my POV it depends a lot in your situation
Example:
You don't have much money to buy some expired domains + exclusive IP + hosting and all that and you want to grow wider
Then 2.0 are a great alternative, much less powerful, but an alternative.
And if we are talking about expired & reputed 2.0, a lot better
But if you have a good bag for investment, I will not use 2.0 for quality content. I will spend every single buck in good content for my own expired domain sites, and use 2.0 as a tier 2 with poor quality content just to help rank all the tier 1 sites. But this obviously means A LOT more money.
Conclusion: If you are starting use them as the first lever.