Hi Ken,
This is something I have been thinking about a lot lately too. There almost doesn't seem to be one "true" answer when it comes to these things. What I have settled on is this: an English (in terms of discussing these differences) is separated by its balanced base of Virginia(s), and then is "spiced" and "smoked" with "Orientals", i.e. Turkish or Greek tobaccos, to varying degrees and presents usually in the "layered" voicing of these basic components. A Balkan, on the other hand does not have a base of Virginia, but a base of Latakia, which is paired with "up front" Orientals, and then Virginia(s) are used to "fill in the cracks" and smooth it all out.
There is a lot of confusing talk about "smoky" english blends (which brings to mind Latakia), and "Oriental" heavy Balkans. These things are true, but to me, in the same way that BBQ Chicken tastes like BBQ sauce. Yes, that flavor is very present, but...its on CHICKEN! So, While the orientals are talked about in Balkans, they are not "heavier on" Orientals, as they are mostly Latakia. And People go to English blends to get a "latakia hit", but, they only have (say) 3 oz per 16oz Latakia, while the Balkan might have 8. So, in English blends the oriental is just a "spice", but when you spice Chicken, you TASTE it. And Balkans have very large proportion of Latakia, and oriental, and probably have MORE oriental than English blends in a lot of cases. So, maybe one could argue that its about the role of the Virginia more than anything, when you think about it. Hmmmm.
An English is a a smoked chicken breast with greek spices. A Balkan is a spicy smoky stew with shredded chicken in it.
I think I remember William Serad talking about how solid and proper Virginia blending proportion is the real foundation of a successful English-though it is not the most "in your face" part. And that Balkan Sobranie is HALF latakia, but the perfect tuning of yenidje leaf is what made it...'what it is'.
Or, forget EVERYTHING I've just said, and look at it like this: English Blends are focused on the blending of a Virginia, or blend of Virginia with Latakia, and then "spiced" with oriental A Balkan is about blending Latakia with Orientals, and then "spicing" or rather, "filling in" with Virginias.
And Scotts? In my mind they are Virginia blends that are lightly smoked up by Latakia, and are usually cavendished. I don't find a very oriental sense to them, thought I think there is usually a little there.
I know I spoke definitively up there, but honestly, what do I know!! These are just my impressions and understandings.