No, neither will lose any data. Always a good idea to make a copy just in case, though. Make a copy of the Games folder and place it somewhere else, like your desktop, before you run the repairs. Default location is D:\%WindowsUserName%\Documents\SimCity\Games
*edit: if you're playing online, all your save data is on the server so this will probably be empty. Online data is C:\Program Files (x86)\Origin Games\SimCity\SimCityUserData - can safely delete this folder and the server will rebuild it on logon.