Working prototypes trump all theory.
I heard all silicon valley gurus stating they were "bearish on VR, bullish on "AR". This proliferated as a mantra throughout the industry. I thought they were wrong then, and believed the opposite - because I had a working VR headset that was awesome, but had only heard somewhat meh things about existing AR prototypes.
Until great AR hardware comes out, I'm still sticking with the same opinion.
Though there has been some progress since then.