Splitting Tables in MySQL. Good practice?
I think everyone is over-complicating this.  The key point here is:


  Combined, the tables have probably 100,000 rows and the growth rate is relatively low.


This is a piece of cake for any RDBMS to handle.  Go with one table, index it properly, and consider it a solved problem.

You don't need to consider partitioning, whether "homemade" or otherwise, until you start handling extremely large volumes of data--think billions of rows and up.