That will always be the way. The 2300 will pick up the very small gold the 7000 will not even see. Two completely different machines.
The 7000 is primarily larger and deeper gold and the 2300 shallow and very small gold.
People tend to have both if you can afford it. Mind you the 4500 with the right coil will also pick up fine gold. For example the small sadie coil will pickup very fine gold.
And really when you start to getting very fine gold it is alot of digging for not much.
Personally I prefer digging less but finding larger gold. Mind you it may be a while between drinks
GPZ = $9700
GPX= $3400
SDC= $3400
That is alot of gold you can get for $6K mind you I would love a GPZ but know well out of my price range. (so I have told)
Cheers
HH