my buddie has bent or broken every seatpost he has owned. hes not heavy but he is just an animal with his bikes. i guess it depends on what you are doing with your MTB. are you just riding it on smooth trails or using it for the road or some heavy duty off road riding. for most occations the thomson post will work great. i was still 290 - 300 when i bought a thomson for my MTB and i am not nice to it and it works fine.
If your my buddie who breaks everything then i have a good solution for you. it adds a few pounds but my buddie bought a solid piece of round bar and either used epoxy or JB weld to bond it. has not had a problems since
