In most cases, no. There are still a lot of people who think that fiber-based TV services like FiOS and U-Verse have better picture quality than cable. There was a time that was true… no more.
In the mid-2000s, satellite services were stretched to the limit. It took years to put a new satellite in the sky and there was a massive demand for new channels. At the time, the MPEG-2 technology used by satellite providers required more than 12 megabits-per-second to achieve signal quality on par with broadcast. At that time, fiber-based services had the advantage. Fiber to the home had a much higher capacity and sending a full-quality signal was no problem.
Satellite services started overcompressing signals. In the case of DISH, they employed a technique known as “HD-LITE” where the resolution of the signal was cut to 1280×1080, meaning a significant cut in quality.
However, today most satellite signals use the MPEG-4 compression standard and are broadcast at full resolution. There is practically no difference between a cable and satellite picture. In some cases the unprocessed cable signal will look better, but in many cases the recompressed satellite signal will actually look more pleasing to the naked eye after being reprocessed to improve clarity and boost color.
It is a fact that both DIRECTV and DISH still overcompress and cut resolution on standard-definition programs. In many cases the SD signal is cut to 480×480, which is still better than VHS quality, and compressed to fit a 1Mbps signal (Keep in mind a DVD using the same technology is 5Mbps.) Both carriers feel that their HD selections are so vast that most people will rarely even see SD television, and that since SD televisions are smaller in size, the loss of quality won’t be as obvious.
There are going to be specific cases where the picture quality of one provider is better than another, but for the most part all major providers give excellent picture quality.