Needless to say birds like more space to move around and as such one should not strictly confine to the size prescribed for the pet. It is always advisable to go for the largest size available in the market to see that your pet has always the luxury of freedom of maximum space.
While considering the shape of the birdcage one needs to remember that most commonly found cylindrical cages are not the best suited for these small flying creatures. Lengthy cages facilitate horizontal flying often preferred by the small birds and as such is more important than the height. Birds seldom fly up and down. Large birds like parrots need to be provided with cages taller in size to suit their habit of climbing up as a routine exercise. The large birds always deserve spacious and bigger cages. Although the cage manufacturers are aware about the danger of incorrect wire spacing of cages, and take adequate care in this aspect one has to ensure that they are uniformly and adequately spaced so as to avoid any danger to the birds by getting caught their heads, wings or beaks inside the wire or bar.
Some of the larger birds like parrots would be best housed in cages with horizontal bars enabling it to climb up with help of their beaks. No such specification need be considered for smaller birds like doves, finches and canaries.
Though price of the cage is always a factor to consider when buying a cage one should not go for the bird cages made of cheaper materials as it may turn to be hazardous for the pets. One has to ensure that the cages need be made of non toxic materials like stainless steel, or powder coated iron that are harmless for these species. Cages that are made of galvanized wires containing zinc have to be avoided. The design of the cage should be such that it allows easy cleaning and maintenance. Certain peculiar shaped cages though gives a different look causes problems for easy regular cleaning of the cages that is of paramount importance to keep the birds healthy and hygienic.
The spacing of the bars or the material used for the cage is not the only factors that matter. The doors, latches and similar parts of the cage should have a fine finish not to endanger these lovely pets.
In short, choosing a right birdcage takes time and it is worthy spending some time and thinking that would lead to a healthy life, security and comfort of your dear pet birds.