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No. 3 gives you very little fore-aft adjustment due to the spacing between the lateral clamp bars - it's the same type as the one I've got on my Brompton, and while it's reasonably easy to adjust (access to the front allen key is a bit compromised) it's the least convenient of the three IMHO. The first type's fiddly to assemble first time round, but after that it's really easy to use. Don't know about the second type.
Shopping for a Tai-ti seatpost: are any of these clamp designs better or worse than others?