Seatposts do feel different to some people, but that part is mostly objective. We have posts made of different material combination to appeal to different people. The main qualities -- in my book -- are lightness, expense, visual, shock absorption, and durability. The quality of the machining and the way that the post is put together is a big issue for me. Thompson seatposts, for instance, are heavier than many expensive posts, but have cleaner lines and have a known durability.

AND: Jabba reminded me of the obvious difference between many seatposts being that they have different clamp technologies employed. Some people could care less, but many have (least) favorites.