2 is the closer one. Cover up each building, one at a time, only leaving a small area of the edge of each each time. The black edges of building 2 overlap building 1 when building 2 is covered whereas when the opposite happens building 2 still overlaps buildings 1.
Or 2. Or... Both? No its 2.
Grrrrraaaaaahh @_@
<this is a reply to your next comment but I hit limit>
Ah, ok sorry. Good point