When to use Managed Metadata service in Sharepoint 2013 and 2010

Question

Hi Folks,
I have been working on sharepoint from quiet some time now. I have been using managed metadata service also.
What I have not been able to find out so far is when should I be using MMS.
What are the real advantages that I can draw out of it.
I have one application that has Managed Metadata installed and has various terms stores and terms. 
The Managed metadata service  created is utilized in search,
What I do not know is what is why are we using it at all. 
What is benefit of it.
Managed metadata service could also be used in navigation is what i know.
But what confused me is when is the best scenario to use it for navigation.
Why can we not use the navigation provider in the managed metadata service. 
There might be other uses also, but that is not clear to me.
Can any one tell me why and in which scenario to really use it.
I know how to configure the mms and how it works though the jargons around the managed metadata.
Regards

Answer 1

Managed Metadata has some specific advantages that make it useful for certain situations.
A managed metadata column has the following advantages over a lookup or choice column:
A managed metadata term set can be shared across the entire SharePoint farm, so you can use it in different site collections.
You can set up "synonyms" so that multiple similar terms resolve to the same underlying piece of information
Terms can be hierarchical (terms can be nested under other terms), and the SharePoint interface allows hierarchical filtering. For example, if I have a term set for Location, and one of my terms is North America, with terms below that for United States,
Mexico, and Canada, I could choose to filter my list to show me all records with any North America location (inclusive of US, Mexico, and Canada), or to filter on a specific term (such as Mexico).
You can allow people to enter new terms, which will then appear in the term set.
You can specify information owners/stakeholders who maintain the term sets without them needing elevated access to sites; normally only site owners can mess with site columns and content types. Managed metadata lets you separate information management
(what terms/synonyms should be used) from site management (granting access, creating groups and lists, etc).
There are some disadvantages too. For example, with a lookup column, the lookup list can store additional columns of information. A managed metadata term set (on the other hand) only really stores terms (and descriptions/synonyms), but not related
info. You might be tempted to do something like create a term set for part numbers, representing every part that your company produces; the term set would handle the part numbers just fine, but wouldn't let you add extra columns of information for
description, weight, price, etc. In such a case, a lookup list is the better option.
Microsoft has some suggested guidelines for when to use managed metadata/term store:
SharePoint 2013:
http://technet.microsoft.com/en-us/library/ee519604(v=office.15).aspx
SharePoint 2010:
http://technet.microsoft.com/en-us/library/ee519604(v=office.14).aspx
A brief summary...
Managed metadata is a good option when the potential metadata meets the following criteria:
​Is something for which a user will select a valid value​
Represents information that is likely to be used multiple times
​Has valid values that can be organized hierarchically
​Includes synonyms or abbreviations that should be aggregated
​Can be applied in one language, but might be viewed in other languages
Managed metadata is not a good option if the potential metadata meets any of the following criteria:
Is represented by a built-in column (such as “last modified date”)
​Has an infinite number of valid values
​Has different valid values in each location that it is used (such as different values for the “version” attribute depending on which product team’s site the item appears in)*
​Has only “yes” and “no” as valid values
*This type of metadata could still be captured in site collection-specific term stores