Well, they are different. "Used to be" is a workaround for the fact that the past tense in English is imprecise, lacking the imperfect past tense. Let's look at an example.
"The pasture was green."
This sentence can have 2 different meanings about the past.
1) as simple past tense, the pasture was green, let's say, a decade ago, but that's all I know. I don't know anything about what happened afterwards.
2) It could also mean that it was green, and continued to be green in the past as I came and went over the years. Or even, it used to be green, but it changed to purple about 5 years ago. In English, there is no specific tense to express this, called the imperfect past tense. One way to solve this is to employ "used to", but this does not work in all cases. Here's an example where it doesn't.
"It was raining all night, when Don Quixote arrived on his horse".
Here, the action is continuing in the past. However, it would mean something different from,
"It used to rain all night, when Don Quixote arrived on his horse",
possibly implying that Don Quixote ended the pattern of all night rains.