I'm using both machines, but am no where near an expert with either. My executive summary would be: The E-Trac seems superior technically, but the V3 seems easier to use. Part of that is physical -- I find the E-Trac tires my arm quickly, where I can swing the V3 all day. (perhaps that is because I swing the E-Trac slower). I also find the V3 multi-frequency and spectragraph systems easier for me than the E-Trac system. I'm a very visual person, and the E-Trac is more tonal. If you are more of a tonal person, you may like the E-Trac better. I haven't done alot of programming with tones on the V3, so perhaps you could set up that way if you are tonal.
The E-Trac seems deeper, in that I've found targets at depths that I've never hit with the V3. However, that doesn't mean anything unless you use both machines on those exact targets.
In one test when I had both machines at the same site, and tested each target with each one, there wasn't a single target that one machine could see that that the other could not. However, the target ID on the E-Trac performed better for me. No target was deeper than 9 inches, however, so it is possible there simply were no targets deeper than 9 inches at that site (I've pulled wheaties at @ 11-12 with the E-Trac at other sites). That said, I could tell whether the target was a high target with the V3 frequencies, even tho the TID was all over the place.
When I was doing that test, I alternated swinging the V3 and E-Trac, so one machine wouldn't have an advantage in knowing the target was there beforehand. What I found was that I preferred locating targets with the E-Trac, and analyzing them with the V3. Take that FWIW.
I think the E-Trac's see thru capability is sweet, where it sees a good target directly under trash. I've never had that happen with any other machine, including the V3, and this was a site that I know has been pounded. That's not to say it is not possible, I've just never seen it.
In terms of programming, I mostly used the settings Angel posted for the E-Trac, but was using a hot running CJ setup for the V3. I think Jack's correlate program performs far better for the V3, and a fairer test would have been to use that, or some other effort at programming (I've tested Jack's program against my CJ mod program, and it is better). I guess the point of this paragraph is that it isn't really fair, given the variability in the programability of both machines.
A couple of things I really like about the E-Trac is the noise cancel and the fact that you never have to worry about ground balance hassles. There is one site along a powerline where I can't even use the V3, but the E-Trac is fine. One thing I miss on the V3 is the ability to mute the machine by pressing the menu button. I like the V3 pinpointing better, but the E-Trac's is fine, IMHO. I like the V3's battery system better. You always know when it is charged.
The elephant in the room for me, however, is the V3 D2 coil issues. I've had 2 go bad, and it is just something I don't want to deal with or worry about, and I don't feel I should have to on a high end machine. White's customer service, however, has always done right by me on this and other issues. No experience with Minelab customer service.
Remember, I'm not an expert with either, but nor am I a fanboy of either. I'm trying to analyze both, and objectively, as best as possible, pick the one I prefer swinging. Right now, if it is a deep silver site with trash, I grab the E-Trac. Any other site (e.g. jewelery sites), I grab the V3, tho I've never really tested the E-Trac hard at a jewelery site.
HTH