Before you can even think about a detector, here's what you NEED to know...
What do you want to find?
Where will you be looking for it?
How much time are you going to spend detecting?
How much money can you afford to spend?
Once you answer these questions you will narrow your search down on which detectors are designed to meet YOUR needs. Once they are identified, then it comes down to personal preference, weight, feel, coils optoins, sounds, creature features etc. Buying an ACE250 or Silver Umax won't do you any good if your primary goal is to find gold nuggets in the mountains of CA. And of course, on the flip side a Minelab 4000 series is overkill for coin shooting in parks.