The Persol 649s are comparable to the 714s in terms of build quality. They feel a little lighter but seem to be just as well constructed and durable. Somewhat odd is the asymmetry in how the stems close - if you close the right before the left they close as normal, but left before right leads to the right stem sticking out somewhat awkwardly. It's a limitation of the frame design, not a manufacturing flaw based on looking at copies of the sunglasses at the optical store. Regardless, they look really cool on a nice dress shirt.
The lenses are excellent - coated on the inside to reduce glare and constructed out of glass rather than polycarbonate. The view through them is very sharp and contrasty and I don't notice any waves in the glass that cause optical distortions. I have the polarized green lenses and for anyone on the fence about polarization, my advice is - go for it. The combination of green and polarization gives the maximum darkening and makes everything look clear and contrasty - especially on sunny days. Side by side with my P3 Plus green glass Ray Ban Tech sunglasses, the lenses on these are noticeably better.
In summary, these are an excellent pair of sunglasses and a pleasure to wear.