You don't want to hear this but they are both good. I don't think there is anything in this world worth understanding where you only have to read one book.
ETA; where do you find the Jean Michel David book? There seems to be no trace of it anywhere!
Good point! And no need to choose then
I read lots and lots of books on RWS type decks. Some of the were good, some of them not so good. I read a few books on Crowley type deck. I did not get a good understanding of Crowley deck and the kabala. Until I read the Understanding Aleister Crowley's Thoth Tarot by Lon Milo Duquett .at Gregory's advise. So I thought I do smarter this time, start with reading only the really good books on the topic.
THANK YOU ALL FOR THEIR HELP AND COMMENTS, I REALLY APPRECIATE IT!
(both books are in my amazon baschet

- the third one, the Jean Michel David's book is expensive even at Lulu (almost $50). I thought to buy the eBook and print it out but since it'is huge (a valuable info found also in this thread) I have to think about it)