William
I have been metal detecting since 1985. I have had 12 different machines. I bought my first Whites PI in 1992. I had two Whites PI machines when I was stationed in Hawaii, so I would always have a backup. Other water machines I have had are Fisher 1280-X, Fisher Impulse, Garret XL-500 and Garrett AT4. I have also used friends Whites Beach Hunter ID and Minlab Excalibur.
If you are going to find gold, silver or platinum jewelry then you will find it more often in the water at busy beaches.
When your primary targets are gold or platinum rings you really should dig every signal or you will miss some good finds. I hope this is why you have decided on the purchase a PI machine. You have to take a lot of what people say for what it is. There are some people that will tell that the machine they use is the very best one, based completely on the fact that it is the machine they use, even if it is the only machine they have ever used. The best machine is the one you learn how to use and use good, as long as it is a fairly good quaility machine to start with. Both the Whites PI and the Sand Shark are good quality machines.
Some time I think about the guys who own Harley Davidson motorcycles. in my opinion they think, if cost the most, and I paid that much then it must be the best. They forget to tell you that their motorcycles breaks more often and cost the most to be repaired. Sorry to get off the subject ... But some people and their metal detectors follow this same line of thought.
So here is my spin on the Whites Surfmaster PI. I have used mine a lot and I am hard on it. Mine has had so much use the paint is almost all gone from the rod. I have had it repaired twice. The first time I changed the batteries at the beach and got sand on the "O" ring, which caused it to leak. I think this was my fault and no longer change batteries on the beach. I will take the machine to my car to change the batteries to and make sure the seal says dry and clean. The second time it needed repair was when it was damaged by movers. I mention this one because I want you to know that whites repair center are great. They have always fixed my machines and returned them in a timely manner and the charges were very fair. When the movers broke my machine, Whites replaced pretty much everything except the rod for far less then a new machine cost.
As for performance I always doas well or better than the other guys I am hunting with. The whites PI will find it if it is there. That includes trash items along with the coins and rings. I always return with a pouch full of Bottle caps, pull tabs, nails, bobby pins you name it. To help with this I always use a good long handled scoop, with a magnet attached to the bottom, it really help with the nails and bobby pins.
With the Whites you have a choice of coils, weighted (zero buoyancy) or standard light weight coil. I have had both and really like the weighted coil, it seems to help keep control of the coil in the surf.
So I don't think you can go wrong with the Whites PI Pro
As for the Tesoro Sand Shark (PI) I have been reading on it and like what I read. I may consider buying one to check it out. I like the fact you can switch to VCO mode or normal mode and that you can adjust what frequency of audio responce you like. It looks like a well built machine and I think it has a life time warranty.
Here is a link I found with a good review.
http://www.tesoro.com/Sand_Shark_Field_Test.html
Here is one for some Whites PI reviews
http://metaldetectorreviews.net/detectors/13-1-surfmasterpipro.html
Also here is a pic of some of my Whites PI finds ( Whites use this pic a few years ago for a add)