Aisle width is a comfort consideration because you can sit with your back to the seat, while your shoulders of normal width almost naturally protrude into the aisle. Otherwise you have to lean forward and turn a little as cart or people move in the aisle, to avoid constantly being bumped and hit. If the person in the middle seat is of greater than average width, sometimes you have no place for your shoulder to go except into the aisle. Less chance of the rear of the FA hitting you as they serve the people in the row across from you. Greater distance from the passengers in the other row is a comfort.

The statistics are what they are, and each reader will have to make their own interpretation. I have never been on an Embraer 170-195, but was surprised at the statistics. I have flown many times on a 777 in business, and three times in coach, but never in a middle seat. Would you prefer a middle seat on a 777 (for sometime upt to 16 hours), which constitute 33% of the seats, or a generally wider seat on Embraer 170-195 with no middle seats (and for mcuh shorter flight)? It is all a personal preference. The more middle seats in the row, the overall less comfort for the entire row. Longer range aircraft with flights of 10-19 hours should give a little more width (& pitch) in coach, simply for health reasons.

Embraer 170-195 – Seat Guru
Pitch Seat Width
UA 31.0" 18.25"
US 32-33.0" 18.25"
JetBlue 32-33.0" 18.0"

Embraer - 19.25 inch aisle width with 18.25 inch seat.
http://www.embraercommercialjets.com...=cross_section

Boeing 777 – Seat Guru
Pitch Seat Width
CO 31.0" 17.9"
UA 31.0" 18.0"
DL 31-33.0" 17.0"

http://www.boeing.com/commercial/777..._sections.html