Which to use is typically not a choice. One or the other will need to be used. They are not interchangable.
If you want to read one key, you would read it.
If you want to read several beginning with some value, use the start and then read. . .
And yes, the specific information IS available thru those links. If you could not find startbr, sauggest you spend some time (more than 7 minutes) learning how to use the IBM documentation.
Hope this helps,