Does anyone know why (or how to explain) why the Bisley model is known as the target model?

I am seriously in the market for a SAA <clone> and trying to decide between the 1851 grips (A.K.A. Navy::standard) and the 1860 grips (larger).
I have a preconceived notion against the birds beak grips and the Bisley grips--without any real data on either of them.
Can someone shine light on the grip choice situation?

Bisley is a range in the UK. The Bisley SAA was named after it.

But why does it have the shape it does?
And why does the shape it have lend an advantage?
And is that advantage only advantageous n slow target shooting?
Or does it translate into other uses?

And, yes, I knew the Bisley was the range in UK.

The Bisley is made with a more vertica gripl orientation as opposed to the standard SAA grips. Take a look at the Ruger catalog and compare the Blackhawk model and the Bisley model. The difference is apparent when you look at them side by side. The Bisley, when properly done, also has a hammer spur that is lower than standard hammers, making it easier to cock with the altered grip style. These changes were done, if I remember correctly, to make the pistol more conducive to target shooting needs of the day.

I have plenty of pictures of them.

What I don't understand is why the bottom-back end of the grip falls away from the heel of the hand,
and why this would somehow improve the hands control over the gun.

I can (however) see how the normal hand grip flaring out at the bottom-back end would help the hand hold the gun up at the front.

I'm sorry I don't remember the exact reasons for the shape of the grip but as I recall it was supposed to allow the gun to "roll" in the hand under recoil thereby reducing fatigue. I am sure a little research will turn up the answer. From a practical standpoint the Bisley just feels good in the hand. When I shot Cowboy Action Shooting for little while, I tried the Birdshead, the SAA, and the Bisley. Of the three, I liked the Bisley the best. It just felt good and more comfortable to me.

44-40Pro is right (both times) and it's why when Lipsey had Ruger make them a limted edition Super Blackahwk in 454 Casull, they spec'ed a Bisley frame.