I see some potential power benefits of running one huge rig versus several though and less costs overall to startup a new rig or expand an existing one but if the rig is higher maintenance long term because of its size I would see these gains being lost due to lost profits from downtime.
For me the biggest problem is mobility, a rig with 6-7 GPUs is a stand-alone box that can be easily moved if necessary. With 19 gpu you are looking at least for a dedicated shelf that will effectively become a "fixed rig"