Gates starts each meditation with a quote. They come from a wide variety of sources, from the Yoga Sutras, to the Gospel, to Twelve Step programs, to Woody Allen, and he even quotes himself at least once.
Which scripture to follow? He says that he has quoted from many sources to underscore how strongly, and how often, they agree. I think if you are looking for agreement, you are likely to find a surprising amount. But it's also tremendously easy to find disagreements, with the right frame of mind.
There's been quite a bit of news in the last few years about putting statues of The Ten Commandments in various places. Preacher's from various sects now seem to claim that the ten commandments are part of some common "judeo-christian" culture that we all share. It wasn't always so. There were violent disagreements between early Protestant's can Catholics about graven images and idolatry, and these disagreements were, at least in part, behind a great deal of violence and perhaps even some wars. (Another irony, as an aside, is that many early protestants would have violently opposed a statue of the Ten Commandments precisely because it was a graven image and smacked of idolatry.) My basic point here, is that sometimes people blow up there differences with each other, especially when those differences might seem very small to outsiders.
On the whole, I think there's probably some truth to the idea that where many spiritual texts are in agreement with each other, they may be onto something important. I also tend to think, in these matters, that age counts for more than innovation. Ideas that have withstood the test of time are more likely to be worth time and effort.