Except that the flashback of young Vito returning to Sicily to kill Ciccio and his men features towards the end of the 1958-60 part of the story.

I think the Saga version is better if you're going to have a GF marathon and watch the whole thing from start to finish. But quite often I just want to watch GFI, which means fast forwarding to the right bit and then changing tapes part way through.