The new offline map area is much larger; about 450mb for all of the GTA and up to around Huntsville in a single download. But now you can finally start a navigation search without having a data connection. I don't have a data plan, so the old offline maps were interesting but not actually very useful.
In previous versions you could kind of navigate with the offline maps, but you had to start the navigation while you had an internet connection. And if you went off course the route recalculation also required internet, so the new version is much better in that respect.
However, I just got a notification that my offline map had expired, even though I only downloaded it a day or two ago. All of the offline search/route features immediately stopped working until I downloaded it again. That would royally suck if it happened in the middle of a road trip, so I'll be keeping the Scout GPS app (used to be called Skobbler) installed, even though it is less convenient to search.