New A/C in burned out Townhouse - 2 story

[Chris Simmons]

I am buying another townhouse.  I have 2 in the area and am looking for more.  This one is identical to my other two in that it is 2 story, 1450 sq ft, 3 bed, 2 bath.  About 900 sq ft down and about 500 up.  One slight difference is that this one caught fire about 4 years ago.  Other than that it is in pretty good shape.

These two story units were designed with split systems.  2 ton for downstairs and 1.5 ton for up.  Since this thing will get gutted down to the studs and get all new electric, hvac, plumbing, drywall etc....I need help determining if I should go back with higher cost split system or put a bigger system in and either do zones for up and down temp control or no zones.  My normal HVAC contractor (they also do insulation) says we can spray foam the roof line to seal in attic and then one big system, with only one zone will be fine....negligible difference between up and down temp.  

I have talked to others that says I can do zone with dampers no problem while I have talked to others and read online that doing this will be a maintenance nightmare and that I really am better off eating the cost and doing a split system.

Has anyone else had a similar situation and re engineered hvac from split system to one larger system?   What about landlords with 1 story houses that have just one system?  

My main concern is tenant comfort and the resulting comfort I get from not fielding calls from them complaining about the upstairs bedrooms being hot.  They will have ceiling fans!

While I don't have to pay their utility bills, I don't want to trash mother earth either.  There is about a $2500 difference in price between split system and one big one, not including the extra cost of maintaining two systems and eventually replacing two systems down the road.  I intend to keep this property for a long time.  Not any real opportunity to sell for a profit....but great cashflow.