Huck is, in my opinion, way more likeable and down to earth. Huck (especially in Huck Finn) is the one of the two who really has morals. Tom tends to use people and to do all sorts of things (like his elaborate plan to "free" Jim) without really caring how they are going to affect others. Huck, by contrast, cares a lot about people. He doesn't even really want the King and the Duke to get abused when they are caught (even though they deserve it). So Huck just seems way more like a regular and caring person and Tom seems a bit spoiled and self-centered.