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Both have the same resale value, though I personally feel that white would command more value simply for the fact that Apple's early products had were 'trademark white' in color.
 
Based on replies so far, it would appear you cannot determine in advance which will have a better resale value.

Thus I do not buy based on resale value, I buy based on desire or need.

Good luck with the buying decision.
 
Classic apple

Not sure this is going to help anyone decide but here are my thoughts all the same..
Black looks great and I like how it's uniform with all the switches, 3G attenna if you have that model, and the apple symbol on the back are all the same colour. Black also blends in with the screen more so when watching some you tube etc.tot seems to 'disappear' more. A big drawback was I found it shows finger prints and smears more than the white iPad.
White is classic apple and I have a fondness for it because of that having been an Apple fan for a long time now. It also seems to hide finger prints a lot better. While I can live with it and it doesn't seem to big of a deal to me, the white border can be a little distracting sometimes. If only in the sense that it makes you more aware of the border.
Have owned and used both colours ( iPad 1 black, iPad 2 white) and would go for the white again next time. It's a very personal choice though and I don't see one having better resale than the other. In general I think iPads have great resale numbers for either colour.
For me it came down to the white tugging at my heart strings in fond memories of iPods and MacBooks in white of yore. Cheesy, yes, but also true 8)
 
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