If you are grappling with the decision on the correct SSAS model to use for your next BI project, then have a look at Melissa Coates article; Decision Matrix:  How to Choose Which Type of Model Meets Your Needs (Here).

The Multi-dimensional SSAS model has it over the Tabular model right now for some critical corporate/enterprise level features, so SSAS MD is still the pick for complex and large environments. The recent release of PowerView for SSAS MD has given proponents of SSAS MD a bit of boost. However, I believe the Tabular model is the direction that Microsoft want to go, so expect a heap of new functionality in next few releases.