How long do you have to ride?
The Carmichael time-crunched plans are a quick fix for those without much time to train. They substitute intensity for the traditional appraoch of building a big aerobic base through volume. They'll certainly make you faster fairly quickly, but the balance between getting fitter and overtraining/burning out is always fairly tricky and even Carmichael himself says you can't keep on with his plans for more than 8-12 weeks before you have to back off and rest for a few weeks to recover.
So, if you have a specific event to train for that's three months away or less, and only about six hours per week to train, you might try Carmichael's TTIP. If you have longer-term aims, or more time available to spend on the bike, go for something that takes longer and builds a more secure platform of aerobic fitness. Friel's training bible is excellent but isn't for beginners - he recommends just riding around for a thousand miles or so before getting into systematic programs.