What's easier to sell/rent Flats or multi floor units?

[Sovat C.]

If you had your pick, would you buy a duplex/triplex/quad that is townhome style (side by side) or flat style (on top of each other)?  which is easier to sell/rent Flats or multi floor TH style?  Is the valuation the same if all things equal?  I would think TH style would make all units equal and easier to rent/sell vs flat style where the ground floor is less desirable and everyone gravitate towards the higher units?