I do not know the exact change (parts etc) but what I know is the new one (with 16 inch alloys) is more stable and feels less like riding on a cloud at high speeds, and corners better too. This is both in 1.6 and 1.8 models.
This is true as well, Prius and specially Aqua did reasonably well here, other than aging batteries (3 years already spent in Japan), and a known ABS issue (improved in the 2011 facelift), there was no widespread problem in Toyota hybrids here. At the same time these experiences are mostly from big cities, not sure how they will do in the villages and smaller cities.