Tumblr

• Tumblr is very user friendly; with no coding
  experience needed. Simply add content and click button to upload.
• Tumblr gives its users the option to
  incorporate Google analytics so they can track the effectiveness of their posts
  and visitor numbers.

• Tumblr allows users to optimise posts for SEO
  purposes through the use of keywords and automatically indexes them with Google
  search.  

• Tumblr is mostly used for sharing images and video.
• Tumblr is known to have stability issues,
  resulting in a lot of downtime.
• Tumblr posts are difficult to optimize for
  Search Engine Optimization (SEO).

WordPress

• Versatile, can be used as a simple blog or
  for a more complex e-commerce store.
• Free to use.
• WordPress has been in use for a long time and has few stability issues.
• There are many free plug-ins available, improving
  functionality of your WordPress blog.
• Easy to customise the appearance due to wide range
  of themes and design styles available. 

• WordPress can be quite complex to use, making it
  difficult for those without coding experience to take advantage of all of its
  features.
• To gain the full benefits of a WordPress blog,
  users ideally need to use their own domain name and host the blog on their own
  server, incurring extra costs.

Blogger

• Free to use.
• Easy to generate revenue from plug ins
  such as Google Adsense.
•  User friendly. Easy to create and share content.
• Very few, if any, stability issues. 

• Difficult to set up on your own domain name.
• Not many themes or design styles available.
• Limited plug-ins, apart from Google specific
  ones.