The most basic similarity between Hank and Tommo in their respective novels is that they both treat the indigenous people they meet with contempt. Hank is very condescending towards medieval culture and people, thinking of them as primitive and ignorant; Tommo treats his tribal captors as simple people, incapable of higher thought and very easy to sway with actions and words.
The most basic difference between Hank and Tommo is that they treat the two cultures very differently in practice. Hank strives to change and educate the people around him, creating schools and manufacturing to bring the people into his modern century. Hank is well-meaning but blind to actual issues. Tommo, on the other hand, makes no attempt to change the tribe he is captured by, partly because he is enthralled with the idea of a simple life, but partly because he is terrified that they will eat him. He is afraid of cannibalism and the nagging fear causes psychosomatic illness, which keeps him dependent on them for survival.