Considering the distinct riding styles and various terrains encountered in gravel biking, what are the key performance benefits and drawbacks of using internal droppers versus external droppers, and how do these design choices impact factors such as reliability, durability, and adjustability in different environments and conditions? Are external droppers more prone to damage from debris and weather exposure, or do internal designs have a higher risk of mechanical failure? How do the actuation methods, such as mechanical, hydraulic, and electronic, compare in terms of responsiveness, smoothness, and maintenance requirements? What are some notable examples of seatposts that have successfully addressed these challenges, and in what specific contexts or applications have they proven most effective?