I'm not very familiar with the V3i myself, but after some looking thru the forum I found 2 threads related to the V3i and I'm sure there likely are more.
They were being praised when they 1st came out, revolutionary. I heard there was a pretty good learning curve. Whites builds great machines, but I haven't heard much from the owners of them lately.
I havent been able to use mine in 6 years so I have lost out on 6 years of learning. I took it out the other day to play with it and it found a 10K gold ring at 9"
The other day I went to the park play a little more and it was hitting foil and pull tab targets at over 13" I was hoping gold ring from the depth but it was little pull tabs or small bits of foil.
If you want to hear bragging, go over to the whites forum where most of the V3i users post. Nothing on the market is as configurable as a v3i and when you give people something that they can mess with... they will mess with it and screw it up. I know, I did it and got frustrated but now I am ready to learn how to use it to its best ability.