Yeah, the contract thing started the Itasca line from what I have read, and yes some years the Itasca line had more features "standard" but the Winnie could be upgraded for about the same total cost. These ideas bear out in most of the opinions here.
I would buy either but we love our Itasca. The colors are muted blues and browns and I've seen brighter shades in the Winnies. The biggest problem with these older machines is the rot in the walls caused by leaks. We checked and double checked the walls from the inside when we bought ours and it turned out we had a rotten panel in back below the actual house part. It was noticed when we hit a off road hole and cracked it open. But I redid that panel with about $75 in materials and it has been fine.
Also really be on the lookout for overhead leaks. They will do the same thing to the panels up there and really be a headache to fix. These Spirit models are Classic, there are pretty many of them and they seem to be holding up well. You can have a ton of fun with it, especially when you retire. Good luck.