No (clarification--they're not all the same),
Some are better than others, and some charge solid fees for detecting on land they've prepped and scraped for detecting. My buddy just got back from Arizona and he says there's all kinds of guys around with the new Minelabs, plus all the other nugget shooters to boot. He says there's lots of detecting going on, but not with a lot of finds. So, not all claims are equal by a long shot. I've had others tell me that they love to get out in the un-hammered wild areas where there's a better chance of finding some virgin ground--it's still out there. Read about Chris Ghoulson's patch he found a while back--it's quite a story. He found it out in the middle of nowhere, and if he's still doing things the same way, he love to hunt the wild areas.
So, unless you want to pay a hefty fee, you'll probably have just as good of a chance on any average claim, unless you want to pay a premium fee for a processed site.
All the best,
Lanny