Would two 70 pint dehumidifiers work as well as one 140 pint unit?
You crossed the line into industrial

I immediately noticed that a search for 70 pint dehumidifiers yielded the usual consumer tier listings... Target Walmart CostCo Home Depot etc. Different deal for 140pt. It gave my local heating /cooling contractor, damage response companies, and industrial suppliers.

So you have made a qualitative leap. From Yukon to Humvee.  This also affects what the customers are looking for.   


The consumer product wins when you put it in your cart, what happens afterward hardly matters.   The industrial product wins then it has lowest total cost of ownership.  
the consumer unit is built no tougher than it needs to be to be parked in a corner for five years. The industrial unit is designed to be dragged around to job sites every day.  
the consumer unit is absolutely designed to work on lowest common denominator mains power,  probably 120V at 12A max.  The industrial unit,  all bets are off. It's assumed a lot of equipment will be in use at that job site,  and someone will be managing electrical loads. 
it is also assumed that very dirty power will be on that job site, possibly from a generator,  and so the unit will be built for that, and also will have no compunction about creating dirt on the lines. 
as part of the "total life cycle" mentality, the industrial unit will be repairable for considerably less than the cost of a new one. This maintenance may be required.   The consumer unit, into the trash it goes. 
industrial units are often deployed with pusher fans to circulate humid air to the unit, so one unit can service a large area. It is sized for that. A consumer is unlikely to do such engineering or desire it. 
the consumer unit factors for consumer sensibilities in style, efficiency and noise.   The industrial unit, nope. 


These factors, rather than cost, should guide your decision.   

Nothing wrong with arrays of cheap expendables;  Google won the search business using numerous cheap beige box PCs while competitors used top tier DEC and Sun systems. Google was forced to learn to adapt to constant hardware failure.