-
I've got one of these:
Simple, cheap, basic and easy to maintain & service (a full service on mine takes about 15 minutes doing it myself).
I think most people are either in the mechanical or hydraulic camp. Mechanicals need looking after little and (relatively often). Whereas (in my opinion) hydraulics are need bigger (more expensive) services less often.
Like @t_w says, if you've got the cash to spend, go for the Thomson. If you want to do it on a budget or just prefer something that's easy to work on, go for a mechanical.
Can anyone recommend me a dropper seatpost, my specialized one that came on my stumpy has been shit since day 1.