Hi guys 

I think it really depends on how you want your boat to sit while you are fishing.  The Big Angry Fish Team put up a really good explanation on their website recently (see here)

[Edit]
But on some boats it can be very time consuming getting up "forrard" to deploy a sea anchor ..... so mostly we tend to attach it to the transom where we can also keep an eye on it while fishing. 
However if caught in a storm and no practical way to run for shelter, you might choose to ride it out.  Then you would definitely tie the sea anchor off at the bow of the boat to keep the bow into the wind and waves.

cabin boat mostly from the back - if waves start coming over the back its time to go home. from the transom you get a V type fishing area and gives good visual on your fishing.

do you have a picture of a bridle set up?