I don't think there will be a comparison forum.
Comparisons are stupid IMHO, it is a never ending argument, nothing gets decided, there is never a winner. There are too many variables to affect the outcome of each individuals use of a detector, even in the same area or in the same park even with the same model of detector. Results vary too widely not only from user to user, but from one state to the next.
If one person can't get more than 6 inches deep with his machine, he is sure the model is to blame. The detector might be out of tune or the coil might be bad or heaven forbid, it might be operator error, but we all know the later can not possibly be an option............

Some people are more "in tune" with their detector than others and let's admit it, some people just don't know how to hunt for very deep targets, ......... it is a whole different set of rules past 6-7 inches and those rules change from model and make as well as the ground you are hunting in. Now add the skills of the hunter and how well the user knows the detector and everything changes even more.
If someone wants to compare detectors, do it yourself in your ground. Buy a used detector and try it, if you don't like it, sell it to someone else to try. The chances are you can sell it for what you paid for it and you might be out the cost of shipping. You will not be relying on someone else's opinions you can develop your own and make your own decisions.
I think the Views forum is the perfect place for comparisons because comparisons are very much like politics, one persons opinion is just as good as the next.