There's very little evidence, IME, that open source software is any better designed of of higher quality than the closed source software that I've encountered, but OSS does have a higher level of hope of closing issues faster. The more eyes thing doesn't really scale beyond three expert viewers per subject matter. (You really only need one engaged subject matter expert, but people have off days; three guarantees you'll get the equivalent of one.)

The scary thing is we are due for a reckoning.