AVGuy is right--there is no universal answer here. I've actually used both DirecTV and digital CATV, and am now a digital CATV subscriber, but what works for me may not work for you. Here are some factors to consider:
1. Picture Quality. For CATV, your PQ will vary depending upon who your CATV provider is and how strong a CATV signal ends up at your doorstep. Some houses are served by plant with a lot a wire and step-up amps between them and the CATV co. That isn't good. CATV can also go out, depending upon whether they use buried lines, etc. For satellite services, your PQ will vary depending upon how well you can tune in the satellites they use--do you have a clear shot to geosync orbit over the equator in the latitudinal slots your satellite company uses? Is there foliage in the way?
As an aside, I hate to say it, but putting an umbrella over your dish isn't going to impact your service quality when it rains and the atmospheric conditions cause signal degradation. Think about it--there is a path between your dish and the satellite. You may cover a foot in front of your dish, but there are *miles* of sky between your dish and the bird. Most people's satellite rain issues, in fact, aren't when its raining on their house--its when the weather front is south of you between your dish and the satellite.
2. Compatibility with Over-the-Air (OTA) broadcasts. Many HDTV satellite tuners incorporate tuners that permit you to attach a UHF antenna and decode OTA broadcasts in HD. You should check
http://www.antennaweb.org and see what is available in your area OTA and what kind of antenna you would need to pick up those broadcasts. In contrast, most CATV set top boxes (STBs) do not, at present, permit connection of an external antenna, so to receive OTA HD material, you would need a separate decoder.
3. DVR Services. DirecTV has just introduced an HDTV version of their box with TiVo support. Then again, my CATV company has also introduced, in the market adjacent to me, a CATV STB with HD DVR functionality. Given the relatively little amount of HD content available, being able to use DVRs compatible with HD seems, well, a bonus. Then again, the retail on the hard to get DirecTV HD Tivos is about a grand. I can rent my STB from my CATV Co. at $5--and keep swapping it out for upgraded versions--for almost 16 years for that amount.
4. HD Content. My CATV company has more HD channels than DirecTV. Your CATV company may not. The HD channels your CATV company chooses to carry may not be the ones you want to see. Again, this is going to vary with your local CATV company. I think ultimately CATV will win this one vis-a-vis satellites, simply because the have the capacity on their plant to carry a lot more HD, as more HD channels are available.
5. Broadband. I get my broadband internet via a CATV modem. I find its faster and more reliable than the DSL service I previously had. Actually, when I was looking, I couldn't get DSL at my new place. But, packaged with digital CATV service, you get a bit of a discount on broadband internet services. That you really can't do with DirecTV, although they used to have a DirecPC service.
6. Digital Audio. Dave, with all due respect, your point about digital audio is STB dependent. My STB converts all the analog stations "low" on the channel tier to digital and passes that through the coax. I get sound via digital coax no matter where I am in the channel line-up. This is manifestly not the case with all STBs, however. Since the low end material isn't digital to begin with, however, you probably get a better audio signal through the analog outputs of your STB than you get out of a satellite box that has converted the analog to digital. For regular TV, I just don't care enough about sound quality.
7. Channel Switching Latency. I seriously dislike the latency of channel switching on DirecTV. Due to the encoding and the odd/even transponder issues, the boxes have to wait until a full frame gets transmitted (as opposed to updates) before they can display a picture. I found that annoying--my CATV switches channels a *lot* faster.
8. Coax Runs. My CATV comes into my garage, goes into a 1:8 splitter, with one of those going into my CATV modem. The other seven runs provide CATV to the various rooms of my house. Satellite generally isn't that easy, and may require multiple coax runs. This is something to think about unless you have easy access to wire rooms. For the new HDTV Tivos with DirecTV, I gather, you ideally want *four* runs of coax. Splitting the signal to other rooms, in addition, also requires multiswitches, not just a signal splitter.
9. On-Demand Services. One feature of my CATV service that I really like is on-demand. I can call up any of the movies currently making the circuit on the premium channels I subscribe to and start/pause/stop/ffd/rew to my heart's content--all for free. Not available from satellite...
10. Ugly Dishes. Satellite requires satellite dishes. I think they are ugly, you may not. While your HOA can't really prohibit you from putting one up, they can also make it difficult.
Good luck!