Every PI I have used will out perform a VLF in heavy black sand. It really comes down to performance and cost of a specific PI.
In order of the ones I have owned: the Whites 500 PI was my first I sold it and bought a SurfMaster Pro. I saw and liked the dual tones of the Garrett Infinium - great success with the 8 inch mono coil over an 7 year stretch, then the Garrett ATX hit the market and read the improvements over the Infinium - I had to have one and have not seen anything like it since.
My major PROs of the ATX: Dual Tone, Iron Check, Auto Frequency select, Re-Tune, sensitivity and audio adjustments, compact-ability for traveling, changeable coil size and headphone.
My CONs: shaft cam-locks require extensive cleaning and can be difficult to loosen, weight out of water (I use the Minelab ProSwing 45 when I use the ATX out of the water), the coil is rear mount - not center mount, learning curve, oh yes the location of the Iron check button - it is hard to push and hold with 31" gauntlet gloves on. BUT it is a BIG improvement over the turning of a know that is required on the Infinium. HIGH Cost: it just took longer to pay for itself than the other detectors at a third the price.
Of the PIs I have used the Garrett ATX is the easiest to adjust while detecting - all push buttons, the deepest "seeing", and most sensitive to small gold. Of course, the sensitivity to small gold (nuggets) is what the ATX was designed to be best at. I still own the SurfMaster Pro and the they still have a use in my arsenal. The SurfMaster Pro for its light weight and the Infinium for its 8" mono coil.
All this being said, I use the PIs mainly in the salt waters of New England. I find the Minelab Exclaibur better in the water of Florida. Each detector shines over the other in different locations. Visit a club near you and ask them...they will have more local knowledge of the area you are planing on detecting with a PI and other opinions on detecting.
