Glen with regard to relative extension and/or headroom in the bottom octaves I'm pretty sure I get what you're saying –too many other variables, but let’s do apples for apples. Could you give an example of in a given manufacture’s line where when the woofer size goes from 5 to 8 they don’t compromise on either extension or level or ball park distortion
I think you meant the compromise in the other direction, from 8 to 5

. Not picking on a simple typo, just making sure we understand each other is all.
Apples to apples, specifically 8" to 5" in a nearfield, I can't say I know of one offhand. But then again, apples to apples is not the point I was trying to make; in fact it was specifically that when comparing apples with oranges, woofer size alone means nothing,
If you want to compare same manufacturer, but look between two lines in the same manufacturer, let me ask you, which is the better LF spec: the Mackie HR624 w/45Hz +/- 1.5dB or the MR8 w/40hz +/-3dB?
But all this talk is missing the real point, IMHO.
The only reason so many people are so keen on trying to peg how speakers sound by some simple quasi- metric such as woofer size - or frequency response, brand name, or smell - is because they do not trust their ears. And frankly, if they can't trust their ears, then what monitor they wind up buying is really quite irrelevant, because their mixes will be unreliable regardless of the speaker.
OTOH, if you got the ears, you're not going to give a shit about woofer size - or any of those other quasi-metrics, because you'll just pic the one that fits your ears.
So, when you look at it that way - which is really the only relevant way to look at it - whether you got the ears or not, woofer size doesn't matter when it comes to choosing your monitor. It's an extraneous and unnecessary complication in anyone's decision process, and a debate that spins it's wheels and goes nowhere.
G.