Equipment that makes the most money per hour and/or has the tightest delivery schedule must be fixed first. But what happens when you must choose between money per hour and a delivery deadline? How can you balance revenue against scheduling when prioritizing resources to simultaneous downtime situations?
Maintenance people generally cannot win when making such decisions. A common solution is to divide up resources so that techs are running back and forth between the two situations. That makes both downtime problems last longer. Focus the right people on the more critical problem first.
How do you choose which problem is more critical? Obtain that decision from the production supervisor. Once you assign the work, get written confirmation of the decision from the production supervisor. Later, if upper management is upset over the missed delivery deadline or the revenue hit, the maintenance department has some protection.
Dispatching only top techs to critical downtime calls is not a good long-term strategy. Trust (but verify) competent and qualified persons to do the job right. This ultimately builds a stronger maintenance department.