I am trying to figure out the difference between the 614FF ,614FS ,and 614FF-E.

I am using a Futaba 4PKS-R and need to pick up a couple of additional receiver's but not sure what the difference is between these.

Thanks for any insight!

614FF - Single antenna
614FS - Dual diversity antenna
614ff-E - Meant for electric. internal antenna only. no visible antenna wire coming out.

Any benefit to the more expensive 614FS over the 614FF-e in an electric vehicle?