I've seen a window that was shattered but intact on a 58' Marquis from 6-8' seas, no impact. To be honest, I know everyone is installing them, but my opinion is it shouldn't be done.
This is the first boat we've had them on and the thing is we didn't know we needed them, didn't miss them on the other boats. I've never had a problem seeing through the size portholes we've had. Plus people generally go to their staterooms to sleep. It's trending. Probably insignificant risk.
Well, do you appreciate them? Will you miss them if the next boat has small old fashioned port holes?
No. No. They filled a need I didn't have. Now, not having them on this boat would require quite a bit restyling to achieve equal style.
With this new fad for huge windows in the hull, I'd be worried about going along-side on some docks. A few 3rd World docks and fueling areas have old tyres, hanging chains or solid rubber commercial fenders to pull up to. No matter how many fenders you put out, one of them could find a way of hitting the window. I wouldn't want them on a 'trawler' style yacht.