Being an off and on user, I only have 3 detectors. The AT Pro was my first waterproof model and introduced me to the fun of mud and creek and quick hunt forays. I got involved trying to find underground electric lines (shallow) and water lines on my farm and some were too deep for the AT Pro. Also, on salt water beaches, the AT Pro was a bit erratic. Of course, now there are a number of new first detector models around.
Deciding I'd rather have one versatile detector over several specialized models, e.g. Excaliber, I bought the CTX 3030. It is heavy, but I usually use the vest with double arms and clip a shovel/scoop on one side and the detector on the other.
While not used all the time, the GPS mapping is really nice when you're returning to large areas as you can review the previous findings at home on your computer and plan the next foray at leisure. It's great in Salt water and, to my thoughts, can be easily used with the default settings while allowing you to easily narrow the search when looking for a lost wedding ring, etc.. I generally want to hear everything as I like old iron tools, silverware, pots, farm equipment, etc. I'm wanting to have a pretty good idea of what's below on my old farm. So far I've found three old, pre 1860, foundations, 7 buried cans, buckets, barrells, on top of the broken water lines and electric lines. The GPS mapping helps to find patterns when you load it on a map at the home computer. I'm very happy with the wide range of the CTX 3030.
While deeper probing detectors sound good, the increased depth of the CTX over the AT Pro has required deeper digging. Instead of dozens of 6-8 inch holes, imagine dozens of 8-14 inch holes in one day... And I've found a 55 gallon barrel buried with the top 3 foot below the surface which I finally gave up on retrieving since the gophers fill the hole back up everytime I stop. Maybe with a backhoe, someday I'll recover that. I've accidentally found a Mammoth Jaw in a mudbank while digging a deep signal one day. No, the bone itself did not signal, but some trash near it led to the dig.
It is heavy, so you may want a smaller lighter model for quick hunts, but I keep using the CTX due to it's easy to use interface (yes you can make it complex, but you can use the standard settings or slightly modify them easily too). With the vest, I don't support the detector at all. It's set and balanced to be almost weightless and allows both hands free for phone or blowing your nose.
Joh