Comparing tabular model DAX with multi-dimensional MDX

Not only is the architecture different for the two approaches to using Analysis Services; so too is the underlying language.

An example of DAX

Suppose that we want to show the total value of transactions in a pivot table (that is, we want to sum Price * Quantity):

This pivot table shows the total quantity sold, and also the total value of all transactions.

Here's a DAX formula which would give the total value measure:

A typical DAX expression, giving total price * quanttiy.

An example of MDX

Suppose we want to calculate the transaction value as in the above example.  Here's an MDX calculation which would create the necessary measure:

A measure in MDX to create the expression for summing.

As this shows, neither DAX or MDX look remotely like SQL, although DAX has a lot in common with the Excel formula language.

Which is better?

I don't claim to have built huge models containing terabytes of data, but reading through other blogs, it seems reasonable to state two truths:

1. DAX will run more quickly than MDX; and
2. MDX can be used in more reporting scenarios.

However, I think the DAX versus MDX question is a red herring.  You wouldn't choose Oracle over SQL Server because you preferred Oracle SQL to T-SQL, and you shouldn't choose an Analysis Services server model based on the language that you'll have to learn.