The current hierarchy of picture quality for consumer Digital video is (best to worst):
1. Reference quality Blu-ray encodes (1080p, 1080i, 720p)
2. Over the air broadcast HD (720p and 1080i)
3. Vudu HDX 1080p streaming (varies by title encode and bit rate)
4. Netflix 1080p SuperHD streaming
5. iTunes 1080p streaming (varies by title encode and bit rate)
6. Netflix HD streaming/Cable/Satellite HD
7. Superbit DVD/Laserdisc SD
8. DVD SD
9. Over the air broadcast SD (480i)
10. Streaming SD (480i)
I didn't include UHD/4K/2160p because it's not mature yet, and not widely available in terms of sets on which to watch it, and content delivery. When it does become a viable choice, it will push the above-listed choices down in terms of relative quality.
I have found broadcast (including ota which is best) to be highly variable depending on how much bandwidth it's allotted. Sometimes significantly worse than streaming hd, sometimes better. High profile sports tend to be the best.