U-verse uses roughly 5.7 Mbps H.264 compression. Cable is 12-14 Mbps MPEG-2. Let's assume U-verse's H.264 encoders are roughly 1.5x more efficient than MPEG-2. That's still ~8.5 vs 12 Mbps in 'MPEG-2 equivalent' terms.
Unless you know a cable provider doing 4 HD to 1 QAM, U-verse is the absolute rock bottom in terms of picture quality. Some providers do just 2 HD to 1 QAM, in which case U-verse looks even more crappy in comparison.