Unit count comparison between buildings - Is there a preference all things being equal?

[Keith A.]

Everyone talks about acquiring many units/doors but is there a preference if you are comparing two buildings where one building has high rents but low units and the other has low rents with high units.  Assume they both cost the same and have the same expenses and return.  

For example a 20 unit at $500 per door versus a 10 unit at $1000 per door.  Logic would say if the return is the same then go with less tenants but curious of the pros and cons.

Any input is appreciated.