John is your man for those answers. Bill too, I imagine.
The Ace 250 is an excellent detector and I wish they were around when I got started. It really is a nice balance of performance and ease of use for a modern beginner.
But, it IS basic. A high end detector is just that, high end. It offers things the little 250 can't. I used to fuss over my .30-30 not having the same performance as my .30-06. Then it hit me - they aren't the same thing. Simple as it sounds, you have to adjust your actions to each. Simple and effective might be the better course for a kid.
Depth? This one thing is such an em-battled issue, that it would be funny if people didn't take it so seriously.
Currently, the GTI 2500 is the deepest detector available. However, that is in All Metal. Which isnt always practical.
What matters more often than not is discrimination, stability and target separation. The Ace is very good at these things.
I'm a little unsure of your question, but if you want a Garrett detector for a newcomer, then the 250 aint bad. It aint perfect, but little is. Besides, if he doesnt take to TH'ing, you can always sell at a good price and not lose much.
