The data will go to the first index. There are many rules that cover precedence but if everything is identical, the first one will take precedence over the second one. To see what Splunk thinks is being used, run this:
You might also want to read the Configuration File Precedence section of the Administration manual to understand how it works. The rules aren't difficult and it will really help you as a Splunk administrator to understand how they work.
As @woodcock points out, btool is a great way to look out the results of the precedence rule operation.