Very similar features. Remember the Milk has been around for longer and has constantly been improving by adding features such as integration with Zapier and IFTT; enabling attachments from Dropbox and Google Drive; integrating with Google Assistant and Siri; and smartwatches. …
Google Tasks is a much simpler task-keeping interface, and I use it for the most important tasks on my phone. It does not offer tags, priorities, or distinguish between lists/tasks. It does let me star tasks, but does not let me determine the priority levels. I can also move …
I think Remember the Milk is a great tool for managing tasks and information. However, it depends on what the person is looking for. If you are looking for just a simple task management tool without any bells and whistles, this may be a lot, as it has a lot of advanced features (and even more if you go pro). If you are looking for a more robust task management tool with the option to add priorities, tags, categories, and assign tasks to others, this may be more suited for this. It is also helpful for managing lists like shopping lists or project lists.
Google Tasks is a much simpler task-keeping interface, and I use it for the most important tasks on my phone. It does not offer tags, priorities, or distinguish between lists/tasks. It does let me star tasks, but does not let me determine the priority levels. I can also move tasks to different lists, but they can be hard to manage if there are too many, so I generally do not use this feature. For me, Google Tasks is ideal for very simple "I need to write this down" type tasks that are of high priority. It is not a good brain dumping tool because tasks can easily get lost. This is more for those nagging tasks that I want to do and make sure there is an appropriate alarm for. It also integrates well with my Android home screen. However, when I have lots of tasks I want to categorize, or I do want to do more of a brain dump type thing, I think Remember the Milk is far better. I can have more control over priorities, tags, assigning tasks to others, and other robust features.