My pick would be the AT Gold. The true all metal mode gives me a little more depth over the AT Pro. I hunt in true all metal mode in areas where there are few targets, such as deep in the woods. The slight audio blip brings to my attention that a target is under the coil. I can then analyze the target due to it's depth, size, conductivity and then dig/not dig. Now this is using the 5 x 8 coil. This coil gets fantastic depth and separation. The other coil I would use is the 9 x 12 concentric coil. This coil gives much better ID when using both audio and numerical values to establish the conductivity of a target. Once you learn this coil, you can easily ID bottle caps. Of course the other reasons for using the AT Gold are it's water proof characteristics, which allow me to water hunt in fresh water lakes,when it's raining out and a total disregard for fog, humidity etc.
If on the other hand I lives near the ocean, I would choose the AT Pro, mostly because it can be ground balanced to salt, unlike the AT Gold. I would easily sacrifice a little depth for the ability to hunt in salt water, as that's where some of my gold finds would come from. I would also use the 8 1/2 X 11 DD coil over the concentric coil, as it would probably work much better in the salt water.
Now if they incorporated the imaging feature into the AT Series, that would make one sweet machine!
Below is a depth chart using the sniper coil, with the AT Gold in true all metal:disc. #1 and the AT Pro in Pro mode.
