I have been on both courses (a few years ago) and I found them both excellent, but quite different. As mentioned, Peter's was a five day and Paul's was a nine day course.
Peter Sefton has a very approachable and friendly style, mixing between demonstration, practical work and critique/advice. He is a great teacher and obviously knows his stuff. He is also a good businessman, as there are ample opportunities to bolster your tool collection from his handy shop! Fair play Peter.
In terms of achievement, I found that the focus on the basics was just what I expected, sharpening, accuracy, using a range of tools and making different types of joints. Peter's focus on accuracy was very impressive and appealed to the engineer in me. He takes a lot of price in the standards he keeps and instils that in the students he teaches. The course itself is well paced and full of useful details. There is a good balance of classroom, demonstration and practical work. The focus changes through the week from understanding the tools, through sharpening and correct tool use to making different types of joint. The project piece you make is a letter rack, with dovetails and tenons.
At the end of the week I had (fairly) successfully completed my project and was much more comfortable with the basics of hand tool woodworking.
Paul Sellers is a very colourful character. His views are deliberately provocative and sometimes more than mildly offensive. That said, I found him approachable and interesting, even if you sometimes need to 'tune out' some of the bluster. He is very passionate about his craft and frustrated that woodworking is coming to mean light industrial automation in peoples minds. His goal is to try to show how inexpensive and approachable the craft can be. He has furnished most of his classroom with finds from ebay and car boot sales, to back up his beliefs. He does have and use modern, expensive power tools and hand tools, but does not try to push them as the only way to do it, which is quite refreshing.
In terms of the course, there are the usual theory, demonstration, practical elements along with his stories and views on woodworking. He is less hands-on than Peter Sefton, although whenever we went up to him to ask about something we didn't understand, he took the time to answer directly or to use the question as a teaching opportunity for the group (not always a great thing for my mistake...). He does rely on his apprentice Phil to help facilitate the class, but I found this to be a good thing as you had a second opinion on things.
The major difference between the courses was the volume of practical elements. Ignoring the difference in course length, I found the pace to be excellent, by the second day I had probably cut 20 dovetail joints, getting better every time. This rate of activity continues throughout the course. Paul is a believer in repetition as a learning tool and he is right to do so. It works well. We created three different projects over the course, a hinged box (dovetails), a small bookcase (dados, mortice and tenons) and an elegant occasional table (complex mortice and tenons). Each project took about three days to complete and we were left to apply finishes later.
I found both courses extremely valuable and interesting, although they differ tremendously in style. If you want a well paced, detail focused, precision based experience, then Peter Sefton is your go to guy. If you want an interesting, hard working, practical, mini-apprenticeship style experience, then I can recommend Paul Sellers.
Here are links to the courses if anyone wants to see the details:
Peter Sefton Furniture School5-Day Furniture Making for Beginners
Paul Sellers New Legacy School of Woodworking 9-Day Foundation Course
I can honestly say that you won't be sorry with either course, I wasn't.