Email Templates v. Mail Merge Templates: What's the Difference?

A question came up recently about email versus mail merge templates - when do you use one over the other?  What are the advantages and disadvantages of each?  In response, I put together a quick grid comparison of different features:

Feature Email Template Mail Merge Template

Insert merge fields

X X
Insert custom attribute lookup fields   X

Are available to send in bulk

X X

Preview before sending in bulk

  X

Edit before sending in bulk

  X

Place content in the body of an email

X X

Respect do not contact rules

X X

Create personal or organization-wide template

X X

Can be used in workflow

X  

Can be created globally for use across multiple entities

X  

Can be created for custom entities

  X

Requires the Outlook client to create template

  X

Enjoy.