Interesting. That may be true in other parts of the country, but we can get both pasteurized and ultra-pasteurized where I live. Most of it comes from a source in Wisconsin that's only about 2 hours away.
I'm not a milk drinker, but I go through about a quart of cream every week. Interestingly, the Whole Foods next to my work near Minneapolis sells both versions of the same brand (Organic Valley) side-by-side and for the exact same price, which I find a little weird.
What prompted my question was because I happened to notice that the small grocery store in the town where I live only sells ultra-pasteurized versions of the same exact brand and, personally, I don't like UHT cream. So I asked the store manager why is it that they only sell UHT while the Whole Foods also sells conventional pasteurized. His answer, and I paraphrase: "I'm sure they sell a lot more organic dairy than we do. Not many people around here buy it so it sits on the shelf longer."
This is exactly the reason I don't like or buy UHT cream when I can avoid it. To me, a guy who grew up in Wisconsin dairy country, it doesn't taste right. I wouldn't necessarily characterize it as sweeter, but it has kind of an "off" flavor that I just don't care for.