The biggest differences between the two oppos are the ability to upscale to 1080p which the 970 doesn't have (it only goes up to 1080i) and component outputs which is only on the 970.
If you don't need 1080p I would look at the 970 or the newer, improved 970, the 980 which is only 20 more and from what I have read well worth the small price increase. Plus, if you upgrade sets, the 980 does 1080p.
The 980 has both component and hdmi as well as a newly added HDMI port and does 1080p. According to Oppo it falls somewhere between the two models you are considering and might be the best fit for you. I know there is at least one member here with the 980 hopefully they chime in.