Huck and Tom are both white which puts their friendship in a totally different context than with Jim. Tom might have more social acceptance than Huck but they exist in similar societal structures. Jim is an escaped black slave. I don't think Tom is progressive enough to accept Jim in the way Huck does. Although Huck and Jim get a long on a deeper level than Tom and Huck, there is still a big power difference between the two. Huck is white, so the friendship is based on how Huck uses his power over Jim.