I have a PI unit, a Garrett Sea Hunter Mark II. It does have a certain degree of discrimination, ie pulltabs can be discriminated out. I have read time and again where even VLF ( I think that's the right term) users hunting with zero discrimination. And also I have read dozens of times "Dig all Signals". If that is the truth then the PI unit should be just as good if not better tan the VLF units. That was my logic anyway when I bought mine. I attended an freshwater club hunt recently where the CZs were the only machines in use except for my Sea Hunter. There were about thirty hunters present. It was my first hunt, second time ever using my Sea Hunter. I found two prize tokens while several of the CZ (VLF) unit users found none! I felt pretty good about that and I was asked a lot of questions about my detector. One thing in my favor was that no one else could hunt within about ten yards of me because the PI pulse jammed their machines! No one got upset however and in the end they were all interested in how well my PI unit did. I had some problems but not related to my detector, just my lack of experience. I kept losing my scoop because if I let go it would sink and I would have to feel around with my foot until I bumped into it or use my detedtor to find it. I also had trouble pinpointing my target in the murky water. I discovered that since all the tokens were on top of the underwater sand it was easier to put my coil over the target and feel around with my hand until I found it. By the time I figured this out all the prize tokens were gone! My two made me feel pretty good.
Anyway, bck to PI vs VLF units. If you don't want to dig everything go VLF. If you are of the "dig everything" ilk, get a PI unit for the extra depth. Let us know what you find and what kind of machin you wind up buying.
