The TC4400 and T4220 are the most robust for the money without being so heavy as the M200. The TC1100 is definitely a great computer but they may find it underpowered. Unless you have access to the OS, the Fujitsu seems the best deal.
One of the advantages of the TC4400, M200, T4220 is the ease with which you can upgrade the memory and hard drive. Because they are larger, more laptop-like devices, they are a lot easier to upgrade. Having a DVD on the T4220 will be nice as well.