I did some testing of silent search, threshold mode, and also trying to "boost" the signal by raising the threshold to where you could hear it again in Silent Search. Results were interesting, and after evaluating the recorded depths on video needless to say it's threshold mode all the way for me.
I do use Silent Search for say fast shallow clad hunting at a modern site where no deep oldies are going to lurk when I'm in the mood for it here and there. But the primary time I'll use Silent Search is when scouting the woods where I can go for long periods of time without hitting any kind of target. In that situation the non-changing drone of the threshold for long periods starts to get old real quick, and by using Silent Search it'll also save battery life and if I remember right Minelab says you can pick up the sweep speed a bit in SS.
Once I start hitting an area of activity though I'll flip back to threshold mode. Not just because of the depth difference but also because we all know the changing pitch of the threshold is one of the strong points of these BBS units. Nothing like suddenly hearing the threshold change to a high pitch and backing up to see what it might be that you just nicked the coil with and didn't notice at first.
Here's the video testing of the "three" modes...
http://youtu.be/yPBZT41IfvU
PS- First time I saw a real difference in Pin Point mode compared to my prior mucking around with it here and there, is when I was hunting a badly mineralized beach for a while in disc and was hardly getting any targets. Plus, even a coin only 4 or so inches deep often would null out or break up so bad I thought it was going to be iron. I flipped to PP and decided to see what it would do and it was like a completely different beach. In short order I had an apron full of clad and other targets. I've got a remote PP switch I wired up on my GT so I kept flipping back to disc to see how it was doing on targets I found with PP. That's when I was sold. All prior experimenting with PP mode I couldn't see much difference by eye, but when I used a ruler in the foreground I could very well see the difference in depth, and that full volume did indeed give PP more depth. One of the things that had me down on PP mode before was I often hunt at lowest volume and when I'd flip to PP I couldn't hear the target that disc had no trouble with, so I explored the low vs high volume issue for both disc and pp too in this video...
http://youtu.be/G817__EOC8A