You cannot know the level of comfort that is afforded by travelling on cheap flights of an airliner unless you have actually flown on it. One of the parameters of judging this comfort level is the legroom that you have in front. After all, if you are able to stretch your legs in the front of your aircraft, it means that you will much at ease than in those carriers which do not allow have much of leg space. There are web sites which have taken care to provide the information about the airline leg space available for the benefit of passengers who would like to search this parameter, besides of course the cheap air tickets.
Leg space is a function of the seat size and seat size, in turn, has two main parameters: width and pitch. Seat width is quite understandable but you might not have come across the size pitch. This is distance between one point of one seat to the same point on the immediate front seat. For the low cost carriers, whose sole concern is offering the cheap flights to passengers, this pitch is usually around 30 inches and for the first class seating, this varies widely from airline to airline, from 40 odd inches to approximately 90 inches.
The airlines which fly the short-haul cheap flights have most of their seats with less pitch and only some of the seats of greater pitch are offered to the customers. However, the long-haul flights have more high pitch seats, though these are still not proportionately higher than the other variants of seats.
The passengers who are conscious of higher comfort levels can make use of these online resources for finding the flights that offer better leg room along with the cheap air tickets.