Normally the ticking watch which is from the application saying hey I am working on it, in theory it may allow you to do otherthings while it is running or different screens. The beachball is from the OS saying hey this app is demmanding a lot from me and I will not let you touch this app until I am done.
Both cursors represent the obvious, they are processing the application. The beachball represents an application that is OS X native and the stopwatch represents apps that are carbon apps which were upgraded from the old classic Mac OS. Native OS X apps never show the stopwatch.