This poll is stupid.
Greater buying power cannot be determined without knowing inflation and its corresponding rate to wage increases.
Greater unemployment is also indeterminable without knowing the economy at the time. When fast food places were offering well above minimum wage per hour during 2005, they still couldn't get enough labor. Would raising the minimum wage when the bottom paying jobs are already over minimum cause any unemployment affects? Unlikely.
Less unemployment - See above
Higher prices is also indeterminable without knowing the total cost and margins. Just because you have slightly higher minimum wage costs doesn't equate to automatic increases in prices. Furthermore, in reality, there are a great many factors influencing your total costs.
Less competitive on world markets - Questionable. Generally the stuff we export isn't being made or produced by minimum wage workers. Do steel workers get paid minimum? No. Do IT network software programmers get paid minimum? No. Raising minimum wages when the industries of exports are already paying often double, triple or quadruple minimum per hour isn't going to change anything.
Benefits low income workers - That's probably true regardless of any other circumstances, barring reductions in benefits to make up for the minimum.
Places people in higher income tax brackets, I'm not even sure how that would work for people who rely upon minimum. Moving a dollar up on a $7.5 minimum on a 60 hour per week 52 week work year doesn't move someone up a tax bracket. For a teenager, it may bump them from not having to file to having to file.
More jobs go overseas - Again, not the industries that are paying minimum as it is.
More businesses close - See above
Benefits middle income workers - Depends. If it's a side job, sure. Holding all things constant though, it should raise the cost of things like fast food though, therefore reducing benefits to middle income.
If you really want to discuss the real cost of labor, it's in the benefits, the insurance and the associated taxes of hiring workers. Health insurance is unbelievably expense, as are worker's comp and various associated costs that aren't being paid directly to employees.