re: How is it advantageous from a competetion standpoint for Mizzou to join the SEC?

With 10 members, the Big XII no longer plays a title game. Missouri has to play a complete round robin and won't benefit from playing in a weaker division if they stay in the Big XII.

But, to answer your question, it may not be advantageous in the short term, but it beats being left without a suitable conference home, which is a very realistic prospect if Texas ever gives up on the LHN, and takes OU, OSU, and Tech with them to the Pac 12.