Farmville in its current iteration is designed to involve your facebook freinds at every level.
Its reward schedule is blatantly designed to encourage social sharing - basically making players skinner boxes for other players.
Tiny tower on the other hand can be played in entirely single player fashion, without really being bothered by "Oh you need 3 paint flecks to paint window X! 5 windows, 2 chairs, 4 cuboards, 2 cashiers left to open store! Ask your friends for parts"
Farmville is far more diabolical than tiny tower. Its obvious the tiny tower guys are more into making a game, while farmville is just plain sinister.
Ignoring the differences is like ignoring the acting, dialog and artwork in a first person shooter because they're all just grabbing weapons, running around, and hitting the shoot button.