As long as you buy from a proper retailer, AMD, Awesome, Demon Tweaks, TSR etc. then you'll be fine.
All of the leaking issues were fixed 2-3 years ago with revised items. They now work as they should
As for the D vs. G thing, I have seen the data in the past in the form of boost logs and N75 logs, showing the turbo to be working harder to maintain the lever of boost. They don't all leak hugely, some are a lot better/worse than others.... but the very nature of the design means that it will inevitably leak