The WSJ reveals one of the best tools for planning airline travel in a piece called The Middle Seat: Outsmart the Airlines to Get the Best Seat in Coach:
Ordering a cup of coffee used to be a pretty simple transaction: regular or decaf. Likewise in selecting a seat on an airplane: aisle or window.
Now, picking a seat can be as complex as ordering a half-caf, no whip, extra shot, soy latte. Airlines have sliced and diced coach cabins into a hodgepodge of choices. Some coach seats have perks like extra legroom and power ports, often for an additional fee. Others seats are skinny and crammed in so tight they won't recline or lack under-seat storage.
Where others saw tiny tush space, SeatGuru.com saw opportunity. With seat layouts and ratings for 720 different airplanes flown by 100 different airlines, the website has become the authoritative source for cabin information. Using internal research and feedback from fliers, SeatGuru highlights the gems, like seats with unlimited legroom, and flags the duds, like window seats with no windows. Information is so thorough that SeatGuru says airline reservation centers use its site for information on their own planes. (Airlines confirm that.)
It's quite true that your preference for an aisle or window seat (I like the aisle myself) should just be the beginning of the process of seat selection if you want to maximize your flying comfort. For all coach seats are most definitely not equal. If you're a regular flier with status on an airline you usually can snag a exit row seat if you book early enough. But some exit row seats are better than others.
I've used SeatGuru for years. I'll usually open it along with the airline's seat selection page to ensure that I'm ending up with the best seat available. The nice thing is that it shows the aircraft seating configuration for the airline you're flying (they are often different) and they recently added a feature that allows you to input your flight number to determine which aircraft you'll be on. Typically, there are only a select number of seats that are highlighted as good or bad choices. But it helps to have the knowledge to try to land the best seat you can and even more important to avoid the lousy ones, especially if you're on a long haul flight. SeatGuru will also provide info on power options which is nice to know as well.