What do you think it would've been like? Better, worse, different?

Depends on how you approach the answer.

The most likely way we would have gotten the mainland would be if they had gone ahead with their original plan to generate most of the wilderness rather than hand placing everything like they ended up doing on Vvardenfell. So it would have been a few interesting places and a lot of bland emptiness, like with Daggerfall. It would not have looked like TR's mainland project. See this early http://www.imperial-library.info/sites/default/files/imagecache/node-gallery-display/gallery_files/concept_morrowind.jpg.

Now, if they had spent an extra 8 years on development to fully detail the entire mainland, then who knows what we would have gotten. I probably would have still liked it though, maybe more, maybe less. I'd guess more though.

Me, personally I'm glad they only went with Vvardenfell. Methinks Oblivion should only have been set in the Imperial City and let modders fill the rest of the province in.

It would be awesome to get a game from Bethesda which was set in a real-scale city in the Elder Scrolls universe. Maybe a Dark Brotherhood or Thieves Guild game kinda like Dishonored or something.

I was more thinking about a TES version of New Vegas, when its main setting would be the Imperial City and maybe some outside wilderness as well, but would have better quests than in Morrowind. Imagine the amount of choices that the player could make