The Ace 250 gives up very little compared to the Xterras. I had the X-30 for a short time, but sold it right after I bought the Ace because I just didn't see any real advantage in paying twice the price and then some) for what was effectively the same performance. The real cincher for me though was the availability of the small Sniper coils for the Ace, as I like to hunt in the trash. On a comparative basis, the X-30 with it's larger (and only) stock coil caused some masking problems where the Sniper coil would pick out coins in some pretty extreme junk. This is not to say that the Xterra-50 might not offer some benefits in some areas where manual ground balancing capabilities are a necessity, but again, look at the difference in price compared to the difference in performance before judging the Ace as an "inferior" detector. I see guys here on the forums, and a couple I have introduced the Ace 250 to, who just shake their heads in wonder at this little machine and what Garrett has managed to do at this price point. But in-the-field results are what really matters, and I have been keeping close tabs on my finds since buying the Ace 150 and 250, and can say that I am very impressed with it myself, even after being involved in this hobby since 1968 and trying MANY different machines over the years. They are not my "only" machines by any means, but it would certainly be near the top of my list if I had to choose only one machine.....at least for my primary style of hunting.
Like many others, I keep asking myself why I didn't buy one sooner.
Ralph