I came across this wonderful article in the MSDN . Between power pivot and Multidimensional the choice would be quite simple because the moment we want to build large scale DW the ideal choice would be Multidimensional SSAS cube.
Due to the introduction of Tabular model in 2012 and it’s simplicity most of us want to move towards Tabular. I can even see lot of queries related to tabular model in the forum as most of the Mid cab and small cab companies are choosing the Tabular models now. But I would definitely suggest checking the below article as not all of them supports all the feature. The best part of this article is feature comparison.
Before making the model decision please check this Article.