Raise them in both. If/when we buy (err...I mean adopt) a kid or two, we will continue to live between the two nations. Why not? Think of how great it is for the kids. My cousin did it because she was often sent to Engalnd from Seattle for large Boeing projects, and the kids are all the better for it...very cultured, very worldly and open minded.
I'm not saying that doing it that way is "better" than any other choice, or that it is easier (I'm not silly, I know it will make things a bit harder in some ways), but as long as you have the skills, the patients and the ability...why not!!
We would not dream of moving a kid every 6 months, and would try to never move them mid-year, but it is certainly a posibility. The school in the states that our kid(s) would attend is quite small (30 graduating senoirs last year) so each time we returned, they would have the same class mates. Plus, a few of the kids there would be cousins (I have a large family that breeds like rabbits) and others would be friends that they knew forever, since we will be in the States (in my home town) often for visits.
But yes, regardless of which you choose, they both have their good and bad points...of course, you can say the same about living on the East coast or West coast in the states (west coast rocks!!) or the city or a small town. Some of it just boils down to how you choose to handle the situations that will arrise based on the location you decide on.