NO!!!!
Not even close!!!
Cable = most channels analog (quality varies greatly with condition/length of cable run)
DirecTV = ALL channels digital (same quality picture as long as signal strength > 30% or so)
When my neighbor and I switched to DirecTV from our local (Time Warner) cable we had the opportunity to check them out on his new HD-Ready digital TV. Since it took the cable company a few days to pull the plug, we had a few days of overlap to hook both sources to the TV (it has a GAZILLION inputs). Switching from satellite to cable on the SAME channels yielded unbelievable results. The DirecTV satellite feed was sharp, clear, crisp, and had amazing color richness. The cable feed was fuzzy, dull, colors more washed, and we saw significant "noise" in most channels.
The same goes for sound quality - ALL digital on DirecTV, mostly analog on cable