My take on it, after being out of the hobby for over 30 years, is that you set a price range you want to spend and determine what you will be using it for mostly. Then you can pick a machine that will be best suited for your needs. I recently went through this, after deciding to get back "into the game" and when I added in factors like:
availability of accessories
ease of use
available training material (YouTube)
price of accessories
it ended up coming down to the Equinox 600/800 and the Garrett AT pro/max. I finally went with the AT Max for a few small differences that I found preferable. Not worth mentioning though since I could have gone the other way all too easily, because I certainly see the advantages of the Minelab units.
I have a buddy who got the Equinox 600 and we were out detecting last weekend. I like the 600 quite a bit after playing with it. But I still like my AT Max quite a bit too. So far, it's been working adequately (as far as I can tell) on the beaches of Galveston island in dry, wet, and under water sand. I didn't really prioritize this usage in my plan, but it's just a stone's throw away so I decided to go do some beach detecting as well. If I get to a point that I don't think the AT Max is cutting it... I might get tempted to get the Equinox 800 as well. Only time will tell.