I think the biggest attraction for Coda is its lightweight attribute. Supposedly Coda's staking nodes are round about 1953025% lighter than BTC nodes. (1gb compared to 2tb+) - the plus side for Coda being that it is built from the ground up.

For Utreexo, from what I understand, is trying to fit one way of writing a code into another. Its basically trying to create a Merkle forest where a set of characters in a hash can be substituted for something else, and be done so in a way that can be proved faster than it can be hashed. Essentially its a very complicated game of substituting for x in algebra.

Both are completely different and I need to personally look more into Utreexo to understand it further.