Hi, Shumpei.
There are many ways to filter out EMI. You may want to implement the circuits on pages 5 and 6 (to eliminate EMI at the inputs) and pages 8 and 9 (for the outputs) of this article - http://www.analog.com/media/en/training-seminars/tutorials/MT-096.pdf
We cannot tell if AD8603 is stronger than AD8605 in terms of immunity unless we test it. You may consult the Reference 1 of the article above for the RFI test.
Regards,
Anna