WSJ

When choosing a flight, the number one consideration is price. Nobody wants to pay more for an airline ticket than they have to.
Prices for the same seats on the same airline vary widely whether you are buying First Class or the lowest of spartan economy seats.
“You have to look around. Don’t just accept airline prices. You can get lower prices from certain agencies which have bulk deals with the airlines,” says Katrina Roberts of Cooktravel.net, which specializes in discount first and business class international tickets.
Other major considerations should be seat width and seat pitch. Travels can check these on a number of web sites including seatguru.com, seatexpert.com, www.seatmaestro.com  and www.seatplans.com.
If you want a smooth ride, pick a seat over the wings. The safest place on the plane is are middle seats in the rear. Exit seats are a little safer because you can get out faster in a crash, according to the FAA
If you don’t want to be stuck in the middle in a center row of four seats, don’t fly Virgin Atlantic from New York to London.  United and British Airways are just okay.
Coach seats used to be commodities like bananas. No matter which airline you flew, each seat was pretty much the same. according to Scott McCartney in the Wall Street Journal.
“Now that commodity is customized. Some seats are wider and have entertainment screens and power outlets. Some planes have more comfortable cabins with higher humidity and bigger windows. Some rows have a cramped depth of 28 inches for seat and legs; others are 34 inches, with room to wiggle. Fast Wi-Fi, slow Wi-Fi or no Wi-Fi? And economy tickets are different, too. Some lack basics like advance seat assignments, frequent-flier miles and overhead bin stowage, even on what used to be full-service airlines.”
Many good travel agents, like those at Cooktravel.net can give you this information for international flights, but most travel agents couldn’t be bothered. All the information in not in the airline computer systems that they typically use.
Travelers have to dig some of this information up on their own.
New York-based startup Routehappy has  started a business in scoring air-travel options. Routehappy’s website ranks flights by specific scores that compare not just prices but onboard amenities. It even compares different flights on the same route offered by the same airline. But much of this information is not posted by the airlines until two weeks before the flights.
“Its too bad. Many travelers will end up buying something and they won’t know exactly what are going to get,” said Blake Fleetwood, president of Cooktravel.net.