The D-70 has a significantly greater azimuth coverage, I find the D-100 Azimuth coverage is fine for the application I am using it for but should be a consideration factor. The advantage the D-100 has though is that you can more precisely point the camera with the included remote control. If the D-70 had finer azimuth control it would be a huge improvement especially when you are trying to frame a shot.
I use these two cameras for webcast while the video quality is pretty good they would be perfect if they had just a little better white balance when the D-70 / D-100 is not zoomed into anything the picture can get washed out a bit. The picture greatly improves even on minimally zoomed objects. Using the cameras in a low light situation is not the best. The D-70 is supposed to have a higher LUX factor but as I was testing I did not see much of a difference.
Overall I think the D-100 is slightly a better camera but it’s so close your decision is likely going to come down to mounting as the D-70 can be mounted upside down and comes with a kit to do that.