"Are the effects earlier from dry fasting because of lack of hydration or detoxing more quickly? "
That depends. If you have a really good quality water, you should be detoxing quicker on a water fast. But that kind of water is extremely expensive, and the only way you're going to get it realistically is if you have a clean source or some kind of machine to purify water to the correct quality.
One of the reasons I got into dry fasting is because the city water here is so terrible that you can put it through a thousand filters and it will still feel like dead weight in the stomache. Bottled water is better, but it's not good enough to justify buying it all the time.