Here in Oz, there are only 5 major (free to air) broadcasters, all have a HD option & SD option. Often it’s only news and sports which is in HD, and many (recent) movies are obviously SD stretched to HD, or perhaps just heavily over-compressed to fit the bandwidth.
Generally I watch everything in HD, if it’s available, but occasionally the SD channel differs from the HD channel, and the program on HD sucks.
If that happens though, I generally watch something from the server
Summary - HD when possible.
After 6 months, I’m almost over the WOW factor from HD, where you aren’t watching the programming for the content, but are instead pinpointing out the flaws on major TV/Movie personalities. It’s great to see that major stars are as ugly as everyone else
HD just looks real. Having a kickass upscaler in the TV makes SD look pretty good too, but watching programs on an SDTV is like looking through fogged up beer goggles