The only means to compare MIB with Buzz is the fact that both shoot lasers. Didn't Buzz even open first? Anyway, Buzz was built and designed as a dark ride in the league of Pooh or Peter Pan that the entire family could ride together. MIB was built with intentions of it being a major "E-ticket" for the park, complete with a height restriction, in the league of Tower of Tower or Spiderman. I prefer MIB's guns to Buzz's, but overall, even with the "league" difference, I still actually prefer Buzz over MIB, just a little. And the line for Buzz and the reactions from people coming off seems like its doing its job fine.
Haven't heard about a rehab, but just some cosmetic upkeep is needed. The ride vehicles take a beating apparently. Not too long ago they seemed to have replaced the control consoles on most of the cars since they looked new compared to what they looked like a while ago, but I haven't been on Buzz for a while, so I don't know how they new consoles are holding up.