All four will help with mild to moderate losses, but if loss is more severe, choices can be more limited. While size is the most obvious difference, each style has different attributes that are important to consider.
Hearing instruments worn behind-the-ear (BTE) or in-the-ear (ITE) can carry more sophisticated technology and more powerful amplifiers; they are also more durable. In contrast, new smaller models (CIC) reside closer to the eardrum, and that proximity to the inner ear can help deliver a more natural sound quality. Your hearing professional will provide you with a recommendation and rationale thats based on your specific needs and physiology.