Most cloth diaper advocates will get you on the track by guiltying you into them. They will say that you're filling landfills and killing trees and putting bodily fluids in a place they don't belong.
While it is true that disposable diapers do have a heavy carbon print, their creators try constantly to go out of their way to minimize this impact.
I must confess, when I was wearing disposables full time, I didn't bat an aye on these issues. It's not that I don't care about my planet, it's just that I knew that nowadays, they use way less material and less plastic than before, they occupy less volume and, most of all, I didn't have any other choice (no, handwashing is out of the question). I did feel guilty about the prize I was paying, and it was always stressful to having to change one that was not at least 50% full. I felt I was not getting my full 20 cents out of it (and that's if you get them on sale, I could go as low as 13 sometimes) and was always afraid I wouldn't have the money or the time to go get more. I don't feel that guilt anymore, I change diapers way more than before.
They keep reducing their environmental impact in water emissions, material usage, energy use, etc, during the manufacturing process and invest tons of money in new technology for the little ones' safety. I don't think they're just willing to sell out of the sake of selling, but they know more than 90% of babies are diapered that way and they have a responsibility to take care of them.
On the other side, we have plenty of moms that don't care if they have to rinse their diapers 7 times before the first use and all the water and electricity that it implies. In places in which water is a luxury, it may even be more expensive than disposables. Every time I read a mom doing such a think, my stomach revolves. Truth is, you only need to wash them once. I throw them with my dirty pile at the second rinse stage and that's it.
That being said, I still prefer cloth for every day purposes. All that technology can't get rid of the smell, or the expense, or the trips to the garbage disposal unit. As I've said before, they are superior.
It may be that I'm not a strong advocate, I'm just a lazy mom that realized they were more work than a small load of laundry a day and didn't like to see SAP gel bubbles around my son's legs. Toxic materials belong in a closed childproof space, not one layer of plastic away from their curious hands.
So, next time you find someone from the Cloth Diaper Church of Babies, don't let them make you feel like a planet destroyer, ask them to convince you in any other way (and, believe me, they will).