I don't believe N reg aircraft are any more or less safe than those on a G reg. I do know of one aircraft put onto 'N' due to wing spar inspection requirements in the UK.
The vast majority of all owner/pilots on any reg are completely above board, but I do think the 'N' reg in the UK using a company in Delaware/Norfolk can be used as smoke and mirrors for the bent charter business, which costs professional companies and decreases safety. All this crap about "I rent the Aircraft out and the renter provides the pilot (who I recommend) is one way of circumventing the rules and should/must be stopped.