Disc brakes :-caliper orientation

[flyerncle]

http://www.flickr.com/photos/30468413@N03/3598377861/
Have a look at that.
It also depends on wheel size for clearance on the lower wishbone bolt,check were the handbrake cable will be routed and for fouling things and obviously easy operation of the handbrake.
The calipers in the picture are from an Audi TT rear.