Oddly enough, disposable wins:
You may argue, but my Marketing textbook has data from research done by Procter & Gamble on the environmental effects of cloth and disposable diapers:
Raw material consumption (lb) C: 3.6 D: 25.3
Water consumption (gal) C: 144 D: 23.6
Energy consumption (BTUs) C: 78,890 D: 23,290
Air emissions (lb) C: .86 D: .093
Water pollution (lb) C: .177 D: .012
Solid waste (lb) C: .24 D: 22.18
Total marks C: 2 D: 4
Guess it depends on which resources you value more...
And, of course, their research methods may well have been biased. I mean- they're obviously going to want you to buy their disposable nappies. I suppose we should find some independent research....