From what I have heard, there've been some glitch problems with the earlier KO FM RX's, when running nitros. All the problems dissapeared, when shifting to another RX-brand.
This might be the reason for introducing a new RX.
However, these glitch problems might be a rumour. Personally, I havent noticed any single problem with my KR-297F RX in my EP cars.
Schumacher Mi5 - Sanwa MT-4 / RX-462 / KO Propo PDS-2123 - Nosram 5600 X-treme Saddle Pack - LRP SPX Zero/X12 17,5 - Nosram Stealth Touch Evolution - MAAS SPS 9250