The Pro and the ionator EXP both clean and sanitize. They both have the same great general cleaning performance. The difference between the two is their level of sanitizing capabilities.
The Pro is tested and certified to REMOVE greater than 99.9% of harmful bacteria through a spray and wipe process. The Pro retails for $299 and has a 1 year warranty.
The ionator EXP is tested and certified to KILL more than 99.9% of harmful bacteria through a 6 second continuous spray. The ionator EXP retails for $329 and has a 2 year warranty.
If your sanitizing process requires that you KILL bacteria, the ionator EXP is your choice. For $30 more you achieve a greater level of sanitizing and receive an additional year warranty. If you are only concerned with cleaning surfaces and removing bacteria, than the Pro is the better choice for your needs.