I think I think that because the central section of the original ship is trimmer and has the more delicate looking landing pods with the central cradle having more visible space through it, whereas the reimagined ship is a lot more 'filled in' looking.
Sort of like how in Starfleet starship design you get the steady elimination of the slim dorsal on the Constitution Class over the years to something chunkier (on the Excelsior Class) to it's then virtual eliminaton on the Intrepid and Sovereign Classes (notwithstanding slightly design exceptions like the Galaxy Class' flared out cobra head neck) and the second Galactica does away with a lot of the space around the midsection the original had.
I'm trying to remember if Nu-BSG ever showed 'original' Battlestars. I have a feeling they did in the fourth season opener that flashed back to the original Cylon War, but I don't know if there was any great time spent seeing them.
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