There are a number of differences between Eastvale and west corona. Eastvale tends to be larger homes, that are built in 2000 or newer, whereas west Corona can range from the 70's and newer, with most being built in the 80's. The type of people who want to live in west Corona typically work in Orange County and are looking to reduce their commute. Those that move to eastvale typically are looking for a larger house, and quite often it is to have more than one family in the house. Many are also drawn to the age of the homes, since they are quite new. Eastvale can have the smell from the nearby dairies tainting the air a bit, which you can avoid in most of west Corona, but not all.
For a long term investment I would prefer west corona, off Green River, since it is already well established, as Eastvale is having a large turnover in residents, and it is yet to be seen how stable the area will be. Eastvale isnt a bad area though, as I wouldnt mind an investment property in either area. A rental house in both areas could yeild a good family for tenants, and good appreciation potential in the long run.
I currently have a few bank owned properties that are in either area, some of which arent on the market yet. If you are interested, let me know and I can arrange for you to see them.