I have not experienced any other FTO's teaching style but I feel I am getting a good service from OAT. Clearly it is an active learning process though and due to the volume (rather than difficulty) of the work, they recommend that you spend 2-3 hours per evening going back over what you covered that day.
The course material appears to be far more comprehensive than the bare JAA requirements to pass the ATPLs - but then you would hope this would leave you with a better understanding of the subjects. The teachers will guide you through the books and point out areas of importance (you will need MANY highlighters!)
They also have extensive feedback which is made available to you and they have a new online system which is supposed to replace Bristol. However, I seem to be in the minority in my course to be relying purely on that system. Understandably, as it is an unproven system, most of my colleagues have Bristol.
Also - the teachers are available in person, by email or over the phone if you have any queries and I have found them very useful during my revision for phase 1.
HTH