Helia: this is how I see the progression of P&P's work.
Original SHE: Gets the house in order.
Happiness File (HF): expands the SHE system to lives, not just a house, recognizing that outside responsibilities (taking kids to lessons, volunteer & part-time payroll jobs, doctor's appointments) all impact on your scheduling of the housework. Basically they wrote that book because their houses were in order but their lives were a mess.
(I had never heard of this until joining the SHE boards back in 1998. HF was out of print by then but I found one in the first used book store I went to. I figure God was helping me out as much as he could! The book is an absolute gem.)
It sounds to me like Happiness File is the best resource for you at this point in your life.
I haven't read the other books or listened to their original tapes so can't comment on those.
Then, partly in an attempt to fully implement a SHE/HF system for the woman who needed to carry the system with her so she could schedule all facets of her life whether she was at home or at work or otherwise outside the house when an appointment had to be made, they created Bound to Be Organized (BTBO), available in video only, no book as far as I know.
For me it was perfect timing since I had been trying to make HF work with a Daytimer because I needed the portability and professionalism it offered. What better than to let my Gurus who had helped me all along develop the system for me.
From there, some of us went to Flylady (which is basically BTBO combined with the email reminders) and others followed CEO who encouraged the use of stand alone technologies (palm pilots, or just a computer) to implement a system.
And through it all (right from pre-web days on Prodigy) women have been getting together to provide support.
As for which system works best? I think all of them are best for different stages of life. So you have to figure out just what you are trying to master and which system fits the bill best for you at this time.
To point out how important 3x5's used to be to keeping me sane, dh actually designed a counter in this kitchen so my cards could be laid out and there was a permanent home for my box, well out of the reach of little, dumping, hands. To this day, my box still sits on the counter, along with my control journal (and a HUGE pile of other papers!) My palm pilot recharger is also on that counter, logically since so much of my system is now in my Palm. But it is a symbolic place for the charger as well because my 'card file counter' is still where I start when I move to recharge myself and my system.