Regarding Occam's Razor, it
is designed to judge which of two (or more) possible explainations is best. It's what the creator of it explicitly intended to do when he created the Razor.
Occam's Razor was created by a monk named (surprise surprise) Occam. He made it to prove that the existance of a god could not be proven logicaly.
In that situation, the question was "What created the universe?", and the possible answers were "God did it" or "it happened through natural means". Because God is a complete unknown, the Razor discredited it immediately, and instead chose the Natural Causes answer, despite it being less simple than the God Did It answer by a good deal.
The situation here is the same. The difference is that the question is "Why is it that there are ships of a nearly identical design portrayed at radicaly different sizes?", and the answers are either "FX screwup, and they're all actualy the same thing", or "They're different classes, based on a similar exterior design".
From an in-universe point of view, the possibility of FX errors are only accepted if the error contradicts a well known fact. A good example of this is the
Defiant's size. We've seen in countless shots that it's size X, yet in one shot we see that it is size Y. The possible answers here are "The Defiant class has a built in shrink ray" or "someone fucked up". In this instance, the idea that the Defiant class has a srhink ray is absurd, and so we must accept it as an FX error. We do this by assuming it was a mistake on behalf of the director of the "documentary" we're watching. For example, perhaps he took some footage of a Defiant flying through empty space, and edited some other ships into the background to make the scene more exciting for the viewers to watch. Unfortunately, he fucked up the scaling, resulting in the Defiant appearing a lot larger than it really is.
In the instance of the BoP size discrepency, however, we have numerous shots of the different sized ships. As it's a bit of a stretch to assume the director of the documentary fucked with the footage that many times, the logical answer is that they're different classes, based on a scaled-up BoP design.
Which is the reason I'm not going to try and prove it. I like it, it works for me...........in other words "I reject your reality and substitute my own".
And you're perfectly entitled to view the scenes in whatever way you wish and come to whatever conclusions you wish.
When dealing with debates, however, you must adhere to SoD.
"You've all been selected for this mission because you each have a special skill. Professor Hawking, John Leslie, Phil Neville, the Wu-Tang Clan, Usher, the Sugar Puffs Monster and Daniel Day-Lewis! Welcome to Operation MindFuck!"