I'm guessing that you posted this question as legroom may be of importance to you. I can only speak from my own lengthy experience of flying, where legroom is an important aspect, and I will choose carriers based upon this, as some charter carriers especially, are verging on the ridiculous, if you are over 5'6".
Having said that, it is important to appreciate the distinction between seat pitch, and legroom. Seat pitch is measured from the front of the seat back of one seat to the front of the seat back of the seat in front, so for example, a seat pitch of 32", with a seat that is 2" inches thick, will leave approximately 30" of legroom. So for any given airline, the legroom depends not just upon seat pitch, but also the thickness of the seat. Seat thickness varies a lot.
Some carriers have seats that are much thicker than others, so even if they have a higher seat pitch, they still have the same overall legroom.
As for the comment above that 1-2" inches make little difference, I have to disagree, it makes the difference between having your knees pressed against the seat in front, so you cannot move your legs, and are in actual extreme physical pain on a long flight, and having a small degree of movement.
To further compound the issue, how tight a given legroom space will be depends not just upon height, but rather upon the length of your femur (thigh bone). One 6' person may find a 31" seat pitch ok, but another (with longer femurs) will find it impossible to fit in the seat.
My strong recommendation to you is this, if you are tallish or have long legs, you WILL find most charter aircraft extremely uncomfortable, and I would strongly advocate you pay for extra legroom seats, or find another carrier. Sitting for any length of time with your legs pinned tightly to the seat in front, so you cannot move is VERY UNHEALTHY, and extremely painful, causing long term pain to both your hip joints and your lower spine. Neither is much fun whilst on holiday.
For the record, those here who say, that it doesn't matter as much as price, are people who either fly very little, have a vested interest(i.e work for an airline with ridiculously low seat pitch to maximise profit), or are not very tall, and have never experienced the living hell of sitting for three hours with your legs pinned to the seat in front. Sure you can get up and walk about, but that can be difficult on a charter these days, as the CC trolleys are usually out most of the time 'selling things'.
Seat width is also important, but not the actual dimensions of the seat, say 17.5", but the space sideways between the seat. Typically, the seats are more cramped at either end of a charter aircraft, as the actual front and rear of the aircraft taper, and so are physically narrower, so best option without extra legroom, is to get a seat near the middle of the length of the plane, and definitely not at the very first or last row. This is not the case with all carriers, but is true with most charters. Make sure you get an aisle seat.
In short, if it's important, get your travel agent to get you a flight if at all possible with extra legroom (most charters do it, so argue if your travel agent says it is not possible), even if you pay more, it is really worth it.
This only applies to charters. For scheduled carriers, many now have a premium economy class, such as united, Virgin, BA, ANA, EVA, Air New Zealand, and so on. For long haul flights via scheduled carrier, they are worth checking out. Book well in advance, and you will often get the premium fares for not much more than the regular economy fares.