Had both. Currently have DirecTV.
Without question, DirecTV is much cheaper - I'd say 30%+ for comparable channel lineups.
My only disappointments with DirecTV over cable:
1) our whole house is wired for cable. Every room. If we had cable, the same cost would get the cable signal in every jack. As long as your TV is cable ready - you've got cable (except premium - which you need the "box" for). With DirecTV - you need a box to get ANY channels. THey charge you $5 a month per box. So, if you have 4 bedrooms, family room, kitchen, office - that's $35 a month EXTRA that you'd pay over cable. I think this is kind of smarmy.
2) Internet Access. We had cable - loved it. Fast, reliable. With DirecTV, you need to be able to get DSL (the satellite internet is VERY expensive and not as quick/reliable). DSL is great, but unless you have the new fiber optic lines and can get 8 MPS acess, regular DSL is only MAX 3 (I think) or more likely less than that, depending on how far you are. You might not think there's that much of a difference, but let me tell you, there are times when I'd give up the $50-60 a month savings just to have my Cable internet back.