A lot of people ask me, which detector I think is best. That is a very tough question to answer. Its like asking what vehicle is best. If your a cattle farmer, a sports car isn't much use to you. Detectors are a lot like that. You would not buy a pipe locator to find gold nuggets.
First thing you want to consider when thinking about a new detector, is what do you want to look for. If all your interested is in locating gold nuggets, finding a detector will be a lot easer. But most people want to do more than one type of detecting. Myself included, I enjoy searching old mining camps for artifacts and coins. Then the next day I'm on the creek looking for gold. A week later I'm in the dessert searching for nuggets. Right now I own four different detectors.
Different brands and models of detectors are designed to do different jobs. That doesn't mean a detector designed for finding coins won't find a gold nugget. The problem you come across is a coin machine is not designed to handle the highly mineralized ground associated with gold bearing ground. It may work, but your depth of detecting will be extremely shallow and the piece of gold will have to be the size of a small coin before the detector will respond to it. In other words it will work for gold but not very well.
If you want to purchase a detector that will do different tasks, you can. The Whites MXT comes to mind. It is a very good detector for finding relics and it has the ability to search for gold nuggets. Is it as good as White's Goldmaster for finding gold? - no, its not. A detector that has been designed to do only one job will be better at that job than a detector that has the ability to do multiple tasks. That is why there are so many different types of detectors. It comes down to the electronics. First, you can only put so much in that box. Second, the detector companies have to sell detectors, if one detector could do it all, it would have to be priced very high to keep that business afloat.
So how do you pick a detector?
#1 - What do you want to search for?
#2 - How often will you be using it?
#3 - What is your is you budget?
Number one and two go hand in hand. If you plan on detecting 2 or 3 times a year and looking for relics 90% of the time and gold the other 10%, a detector like the MXT may be exactly what you need. But if you are retired and plan on detecting 2 or 3 times a week and you are going to spend the time evenly between coin hunting and nugget hunting, two different types of detectors would properly be your only option.
The more time you spend detecting the more your budget comes into play. If you are going to spend most of your free time detecting, you will want to be using the very best detector you can afford. If you are going to look for coins with the kids on your summer vacation, then put it away until next year, a very cheep, beginners model would be perfect!
The best recommendations I can give is to check around and talk to all the people you can. Look for people in your area that do the type of detecting you would like to do. Find out what type of detector they use. What they like and dislike about it, and how well they are doing. They may love it, but if they are not finding anything it may not be the type of detector for your area. If you talk to a dealer, not all but some will try to sell what they carry. A local dealer has a lot of knowledge and they should be utilized but remember they may want to sell what is on the shelf.
Stay with the major brands, they have been at it for a long time and probably will still be in business in 10 years. The resale value will be much better with a known brand.
Do not rely on manufacturers adds to pick a detector - they all sell the best detectors in the world!
The internet is a great research tool, read the forums, but put more weight in to the people you talk to around your local area.
When you get a detector, read the manual 3 or 4 times. Learn not only how the detector works, but learn why it works. Learn what each knob does, and when you adjust it, what does it do in relation to the other controls
Hope this help, detecting is truly a fun and satisfying hobby. I got my first detector in 1968 and I still love detecting!