Theoretically, there is a huge difference. If management is doing what it gets paid for, we have better cars at better prices and consumers, employees and stockholders all prosper. If UAW management does what they get paid for, we get more expensive cars with lower quality (company has to save money elsewhere). Stockholders, consumers do worse as will many of the rank and file. UAW management does better as their base pay is indexed to the pay for the actual workers. Other people get laid off, not them.
What if things go badly...management gets the boot...many fewer of those jobs to be had (why they make so much). New management comes in and tries to improve things. If they go badly for UAW management, they stay in place until the next election and still draw their big paychecks. Even if they get 'fired' in the next election, they can still be paid big in other roles (almost impossible to be fired).