It's hard to tell since most GPL violations are simply ignored, and most NDAs are secret to begin with. In general, the NDA-spamming companies have more money t

It's hard to tell since most GPL violations are simply ignored, and most NDAs are secret to begin with. In general, the NDA-spamming companies have more money than GPL-defending groups, so from that perspective a real-life consequence could be that the company has to spend money on legal either way, and might simply pick the cheapest route. In some cases (Linksys for example), making a small modification and then releasing everything that wasn't encumbered was enough to solve both issues. In general, breaking an NDA is far more costly than violating the GPL, even if it were enforced like NDAs are.