If the image is noticeably fuzzier, the optical quality is poor. At night view the stars, or during the day look at glints of sunlight on power line insulators. If so, this is an indicator that another binocular might be better. How much is allowable is a matter of taste-sometimes the bowing is a compromise in order to keep the image sharp from center to edge of the field. In astronomy, this type of distortion is inconsequential.
Eyepieces can vary greatly in quality.
Take time to learn their differences, and find what is comfortable for you to look through. Carrying cases are optional accessories with some models. On some models, the hand control for the drive system or computer are optional. Make sure that you know what features are included as standard equipment when pricing systems. You will also need star maps and atlases, and a filtered red light to read them while preserving your night adapted vision.