Seat Width?
 

I remember a while back that JetBlue was advertising that their seats were more comfortable and that they were wider than the competition. Is this actually true, or was it just a marketing ploy?

Seatguru has JetBlue's A320 seats at 17.8" wide.
United's A320 seats are 18"

So, was it a clever marketing trick comparing JetBlue's A320 seats to a Boeing 737/757 series which has 17.2" seats (due to the design of the cabin)? Or are the seats really roomier?

I don't know about actual measurements but they definitely don't feel roomier than E+ seats on UA.

Airbus narrow body planes are a little wider than Boeings, so typically have around an inch more seat width. IFAIK, there isn't much difference in width between different airline's 320 series, but compared to 737/757 (and 707/727), you get the extra inch.

Generally that is the case. But some airlines use the same seats on A320 planes, meaning the extra width is in the aisle.

SeatGuru says Virgin America coach seats are 19", I am not sure how this is possible unless its measured differently.

They might play with the seat cushion width, but the shoulder to shoulder width can't vary much between different airlines flying the same model airliner.

It's an outright lie; they measured from the outside of the armrests.

There are differing ways of measuring seat width and 17.8" is probably correct. UA's are of similar width and they just rounded it to 18." Most Airbus narrowbody coach seats are about 17.8" wide and most Boeing narrowbody seats are 17.2" wide. Some round those numbers to Airbus 18" and Boeing 17" but regardless, the Airbus is noticeably wider. VX is probably measuring from the outside of the armrest or something.

Here's an update on my question.

I flew from BOS to LAS. Rather uneventful flight. I fit into the seat just fine. The 34" pitch was great as it almost felt like I was sitting in Economy Plus/Comfort on UA/DL. The controls in the armrest left a bit to be desired as the buttons weren't always responsive. The seat recline was close to none (there literally was no difference). The headphone jacks were the worst.

On the way back, my seat did not recline at all (I told B6 and was given a $25 voucher) and the headphone jack on that seat was worse. It wasn't as bad as the guy in front of me.... he didn't even have an armrest! It was missing!

There is no standard for measuring seat width across the industry. Because of this the exact same seat could have different dimensions reported depending on who is doing the measuring and what they want to present. Unless someone brings a tape measure on board to compare them in a standardized way we can expect to never see useful measures.