I am looking to buy a new detector and doing some research. Two of the detectors I am considering are the Garrett Ace 250 and the Ace 350. In looking at the spec they seem almost like the same detector except for the frequency. How much difference does the frequency make between the 2? Also, are there any other differences I might have missed? If you have used both models, what is your opinions of them? Likes, dislikes on either model?