I know for sure that 1.5 was shipped on 1.4MB floppies and 1.0 on 800K disks. Outside of that I think the packaging and maybe a few of the features regarding QuickTime, System 7.5 features (AppleGuide, perhaps), etc were updated or enhanced.

Good luck finding any MacWrite--they show up very infrequently on eBay. I was very fortunate to find a boxed copy of MacWrite II this past spring although I had to be on my computer at the last second of the auction to make sure I got it!