Yep - apples and oranges. 

Multi-Dimensional and Tabular will both give you analytical cubes, but both have weaknesses and strengths, choose your type carefully. 
R - best to read up - https://docs.microsoft.com/en-us/sql/advanced-analytics/r/sql-server-r-services
The same question was asked on ... https://datascience.stackexchange.com/questions/5404/how-does-sql-server-analysis-services-compare-to-r

Personal advise, but maybe I would suggest starting with a tabular to unpack what you require from your data, and work from there.