All of SRAM is interchangeable except for short cage derailleurs and cassettes larger than 28t. In my opinion SRAM Rival is a bit much for a commuter bike. I probably wouldn't lock it up outside.

Also, if you're deciding between SRAM and Shimano, go with whichever you like more. The difference in performance, durability, etc. is pretty much the same. It's more about personal preference between the two systems. I prefer SRAM because of the hood shape and double tap.