It is important that you take into consideration how often you plan to use the infuser. If you are the type that makes tea every single day or several times in a day, buying a higher-quality infuser might be worth your investment that could stand up your frequency of use.
Another important tip is on where you typically prepare your tea. If you always drink tea when you are at work, then you might want a compact and portable infuser or a travel mug type infuser. If you always prepare tea at home you might want to own a teapot.
More importantly, be cautious in terms of quality. Since not all infusers are created the same, there are novelty types of infuser that are made of cheap materials. So do not take everything at face value because a good looking infuser might not function in the same way that it looks.
Also, see to it that your pick is easy to clean and maintain. There are several models that have multiple grooves and corners that are hard to clean. If you are the type who prefers ease in terms of cleaning, pick the model that is dishwasher-friendly.