Why do people typically use AP instead of HRP for Southerns? - (Jul/18/2013 )

It looks like people usually use AP antibodies for Southern blot detection instead of HRP. We have reagents for doing HRP detection on our western blots though. Wouldn't it be more efficient to stick to one system in the lab? Is there a good reason people mainly use AP for Southern's instead of HRP?

Thanks.

in general, ap is more sensitive than hrp.

Signal from AP also tails off less rapidly, so you can do longer exposures. HRP is quick and quite bright, but the signal doesn't last.