Who cares about pressure drop. Its a stat that only really matters on paper. Top to bottom front mounts just dont use all of the runners like a side to side does. Make a run with a top to bottom then feel all the runners only a few on the far side will be hot the rest still cool. Thats because the air isnt going through them. Now do this with a side to side and see the difference. A side to side is just better at cooling the air.
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Tom