Given that they have more material in them, I'd predict that the cheaper helmets might be safer than the more expensive ones. Hotter: sure, heavier: definitely, worse fitting: that's a personal head shape thing, but safer (with the caveat that they both meat the minimum CSPC requimrements): maybe.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"