actually, i've got a slew of those early to mid 1977 Rumours shows. The very first "Rhiannon's" of that tour were very similar to the Rosebud performance. Stevie hit the same notes and did the same ending - almost verbatim. For the next few months (till the beginning-middle of June), the performances were still strong but it was slowly becoming evident that Stevie's voice was changing and she was having difficulty hitting the higher notes...It's really apparent on the "all your LIFE" lines as well as the ending...Then, in the Little Rock show, she began dropping down the second high note during the "all your life" verses. Her voice was getting a little more strained and scratchy - but it was still good...just a little more raw....Then, in the MSG show from the end of June, she had a really bad night...it's painful to listen to it....she was almost whispering the ending in a falsetto....she kept repeating "try hard!" "try hard!" at the end....i think that was when she began changing her singing during that song.

The "live" album version was definately from the spring of that year. It's a pretty solid performance. Vocals and all....However, i think that they overdubbed the "dreams unwind" lines until she does the screaming part before the final crescendo...she was doing a very soft rendition of those lines which i don't hear on any of those other era shows. And, her voice sounds more Tuskish to me...We know she overdubbed the "Sara" vocal so it's quite possible. Also, they overdubbed the chorus of "Rhiannon".
In the "live" album version, Stevie is doing the middle part and Chris is doing the high part. When they actually did it live back then, Stevie always did the high part and Chris the middle. I'm sure they just wanted it sound fuller. Sounds good to me though either way.