TomD
There are functional differences. I would break these into catagories:

Functional differences not related to the shaving. These are of two types:

a) outright differences like independant adjustment

b) similar but different, for instance the way it supports the main blade

Functional difference related to the shaving. These could also be subdivided:

a) those that are different. Not the expert on this stuff, but the shaving comes off Japanese planes typically used, differently than it does on western planes. That is probably not something that couldn't be mimicked by other planes, as it is with super surfacers. I have learned a few things in the last few days that I did not know before like the low angle and 80 degree stuff. I was aware it existed, but thought it was structural, and there are some inconsistencies there...

b) Then I think there probably are some differences that we do not know the origin of, what they are for, any more than as Pam says, we know what the western stuff is for. There is a common misconception that by going back and figuring things out, we are coming up with the reasons stuff is there, this is often not the case. However it is a useful technical exercise so long as we don't over apply the results.

Then there is a category of other stuff. I am not a big believer in a number of Japanese tool dictums, Stuff like sharpening on different stones ruins a blade, or that the hollow has a proximity effect on the cut, etc... There are quite a long list of things. I don't know of any that affect the SB, but there are others more into this than me. I keep my mind open when real Japanese carpenters who can work circles around any of us talk about stuff, but I am not blind to the traditional elements. Probably people who are deeper in this shouldn't waste their time talking about it to those who haven't even bothered to try out the tools. Around here it just leads to conflict.