Actually, it's not opinion, it's fact. And this isn't a personal attack, just pointing it out, but if you've got two blades of (for argument's sake) 19", and they're doing sweeps that cover approximately 1/2 of a full circle, that gives you a total area swept of
A (area) = 3.14 (pi) r (radius - 19" for each wiper) square
that gives you an area for each wiper circle of 567 square inches (rounded up) and then halved because it's only traveling half the sweep of the circle. Two of them makes 1134 square inches covered by two wiper blades.
A single 26 inch wiper would only cover 1061 square inches, and it would have to do it in twice the time in order to do it as effectively as two wipers.
Basically, it's why most cars have multi-valve heads these days (the exception typically being pushrod engines). Manufacturers figured out you can get tons more airflow at much lower overall valve lift with two smaller valves than you could out of one larger valve. Think "Japanese" multivalve.
I recall a company called Dominion, they made a multivalve head for the Small Block Chevy, by using a forked rocker arm to actuate the valves. They had something like 1.8" intake valves, and they found that their two valves, at .400" lift, would flow better than a single 2.20" valve at .600" lift. That doesn't just mean that they perform better, it means less valvetrain wear, because you don't have such steep ramp angles on your cam lobes, and it means less valvetrain reciprocating losses, because you don't need retardedly strong valvesprings in order to keep the valves from floating with that much lift at high rpm. Don't know whatever happened to Dominion, but there's a company here
http://www.araoengineering.com/ that does the very same thing.