To be honest I have never used a 5.75 coil model, but I do swing an older 7" coil Compadre.
I also had a few weeks hunting with the 8" coil model in 2013.
Very similar to mine, still does the double beep thing on targets close to big metal, they all seem to be able to do that, still sensitive to just about everything and the 8" coil seems a little deeper.
As far as the discrimination I did notice the slightest hint of a difference in the 8" in the area that I consider my calibration point...zinc cents that come in at 3:00 on the disc area.
Not a deal breaker but a difference.
I have read that many like to calibrate their Tesoros to nickels, using a screwdriver to adjust their disc knob to point to the 5 cent mark on the dial on nickels using mostly air testing.
This would not work at all for me.
Out of all the coins I have come across nickels are the weirdest and "iffiest".
I don't ever thumb the knob up to the fade out point but always turn past that point and thumb down to listen to and also notice where the target comes in instead...a much more accurate way to figure out targets in my experience.
Using this method I have dug a lot of nickels and even though a lot of them have "come in" at that 5 cent mark many have also come in below that Mark and also above.
Not just a few, either, lots of them, so to calibrate to such a jumpy coin to me makes no sense.
On the other hand a zinc cent is the coin I like to see come in at exactly the same area every time.
Not only is it much more stable than a nickel, behavior wise, but there are so many more of them out there that I come across.
On my Compadre 99.999% of the time a zinc cent shallow or deeper, on edge, flat or whatever, will come in with a solid signal and with that knob pointing directly at that 3:00 position.
Dimes, copper cents and quarters won't disc out, nickels are too iffy so it makes sense to use a zincoln for this because I trust their behavior.
On my Vaq it is almost exactly the same but once in awhile a zincoln will be slightly off.
On the 8" Compadre it was the same.
Most were at 3:00 but in the time I had it several were slightly below and slightly above that mark when all was said and done.
In my world the sky us blue, the sun rises in the east and sets in the west and pretty much all zincolns come in at 3:00 on my Compadre and I got used to it so that is that.
I don't believe this will affect its ability to find and identify targets, coins and jewelry included.
I assume the different coils on these two units is the cause for this very slight difference in behavior, but again I mention this is not a deal breaker by any means...just something I got used to after hundreds of hours swinging this wonderful machine.