I own an EL and have testdriven the Rio5. Hands down, the Rio5 is quieter.... Acura adds no more sounds dampening to the EL then the Civic, which is very noisey at highway speeds (both wind and road noise).
The Rio5 was very, very impressive on my highway test. It had less road noise, a lot let wind noise and it tracked straighter in the wind... If anyone knows about southern Albertan winds, then they'll know we like cars that are stable on the highway.
Get the rio5, IMO... 5 year bumper to bumper warranty