Machines that are sensitive to tiny gold like fine gold chains are what you want if you are after that stuff, but I've owned machines known for that kind of small/fine gold sensitivity and they weren't for my particular tastes. Problem was at trashy sites I was being bombarded by hard hits from tiny flakes of foil and other tiny junk, and ended up digging a lot of that stuff because it just sounded so good/solid.
I prefer my Minelab for my type of hunting, because I prefer odd shaped small bits of foil and other junk to sound sick and be jumpy on the ID. That helps me to avoid a bunch of small junk when gold ring hunting. The way I look at it most gold jewlery lost is rings, and when it comes to even the thinnest of gold rings a Minelab will bang hard on it and super deep, so as long as it can do that I'm fine with it having trouble with tiny earings or thin gold chains.
Others might want the fine gold ability and if you do then a Minelab isn't the best choice. I saw one guy who waterproofed a machine known for it's fine gold ability just so he could go after fine gold chains in the water. Different machines for different tastes. You have to decide what kind of hunting you are intending to do. Deep silver coins or even the thinnest of gold rings and the Minelab excells at that and will get them at depths that will make your jaw drop, but fine gold people should consider other options.
Just the other day a friend was water hunting with his Excal. He's dug a ton of gold rings over the years and he digs any signal, sick sounding or not, above iron. Despite that he's hardly ever dug a gold chain unless it had a pendant or a large clasp on it that the Minelab could see. Anyway, he got a large metal signal and was sure it was a can or something, but he scooped it anyway and tangled in the large blob of junk metal was a fine gold chain. He said had it not been hooked on that large piece of metal he would have never found than chain.