The choice between these Apple Watch bands really depends on your preferences, activities, and personal comfort. As such only you can make the final decision on which of these bands will work best for you in the long run. AFAIK. Apple still provides a 14-day return policy should you regret that decision.
Sport Band: This band is made from fluoroelastomer, which feels smooth, durable, and water-resistant. It works best for activities like swimming or intense workouts because it holds up well against sweat and water. The pin-and-tuck closure feels secure, and the material doesn't stretch or absorb moisture.
Sport Loop: Unlike the Sport Band, this one is made from a soft, woven nylon material. It’s lighter and more breathable than the Sport Band, making it ideal for day-to-day wear and activities that don't involve a lot of water as the fabric can stay wet for a while and takes time to dry.