There are a few key factors to consider when choosing a swing or bouncer. Look for ones with harnesses, restraints, and secure straps to keep the baby safely in place. Choose a seat that can be adjusted to multiple positions and grows with your baby. More speed and motion settings are better to suit your baby's preferences. Also, consider soothing features like music, vibrations, and visual toys. Ease of use, cleaning, and assembly are important factors too.