Well, I can only speak for myself but I love my Cortes. I started with an Ace 250 which was a good machine but the Cortes is orders of magnitude better. I find the TID to be accurate at least 75% of the time and even when it is off there are generally some indications that the target may be something other than the indicated item. After using the Cortes for a length of time I find that I don't need to use the Sum feature much, I pretty much know when I'm going to dig a iffy target.
In short, I have found much with the Cortes and am very happy with it. That said, I am looking forward to see what Tesoro is reportedly soon to release. Not because of any lacking in the Cortes, but because of how much I think of the Cortes and Tesoro.