What is the advantage of using D'Alembert's principle when dealing with dynamic systems?

In our dynamics class, it is highly recommend to us to use D'Alembert's approach rather than the traditional approach to solving dynamic problems. For example, consider the problem of a block resting on a surface (we know the cof): Rather than calculating the frictional force of the block on the slope and comparing that to the component of weight acting down the slope, we draw the free body diagram including the inertial force and directly solve for a, which will tell is if the block is moving or not. My question is why this method is recommended over the traditional approach? It seems the answer is usually with regards to making it easier to solve more complex problems, but I don't quite understand why this trivial manipulation of Newton's second law makes it much easier to solve problems?

I'm sorry if this has been asked before, but I couldn't quite find a satisfactory answer online!

• What do you mean by the 'traditional approach'? Your example of 'calculating the frictional force of the block on the slope and comparing that to the component of weight acting down the slope' is a static approach, not dynamic since it does not consider inertia. Jul 20 '16 at 10:26
• Quote from en.wikipedia.org/wiki/D%27Alembert%27s_principle, "The advantage is that, in the equivalent static system one can take moments about any point (not just the center of mass). This often leads to simpler calculations because any force (in turn) can be eliminated from the moment equations by choosing the appropriate point about which to apply the moment equation (sum of moments = zero)" Jul 20 '16 at 13:18