You already know that everyone and their grandma is offering a coding boot-camp to help further your career. I can't speak for the rest of the other services, but I can say that I had a wonderful time with Practicum.
I am currently on the data science course and have added many of these projects to my portfolio which is already being used for interviews. The technical skills are well explained with business and technical examples of why they are teaching such a skill. I did have an engineering background before starting this program, but I believe the exercises are a good extension of what was taught and are not terribly difficult to understand. If I ever had issues comprehending an exercise, the Slack community with other students and instructors was always there to support me.
After each course is a project in JuypterHub which is critical to building your portfolio and competence as a data scientist. The projects have proved to be challenging and excellent practice to what you would be doing in industry work. The projects I've worked on so far was plenty of exploratory data analysis, statistical testing, and some machine learning classification problems. Machine learning problems are significantly more complex and I'm glad they are spending enough time to really have you understand the details instead of just teaching you pre-written code.
Now why did I give it a 4/5 stars? There are a few bugs and typos here and there that have hindered my learning momentum, but I do believe that is being fixed in the beta. My other feedback is that some of the project backgrounds are not that exciting such as identifying what apartment characteristics affect the price. Of course, that is a personal preference, but it does factor in how exciting your portfolio becomes. Overall, I believe the program is great and you should definitely consider it amongst the other services.