I was under the impression they understood each other just fine Sora never blamed Riku for what the darkness/Ansem SoD made him do.
hmm true, if it was to show them the others journey I wonder why then, to see how they deal with the others previous situation? or maybe Sora gets a little cocky and to him its all about winning the MoM while Riku is happy either way.
Guess we'll know soon enough though