They all have their income, bonuses etc. Now there is a strategical factor to those regions.
If its what you claim we should just have 53 territories that we can move in to but we have 183. If we only have 53 real provinces(not regions) how come we can capture 183 regions. Only one city counts now the capital of the province and this has just killed any historical plausibility that game might have had. but in effect cannot be sieged, cannot be defended. With the only difference that now they got a region and some buildings. You only have 53 real regions, infact by the interviews you won't even be able to build several buildings, in a city but you will have to specialize, in that way some cities will work as mines, other as farms, so they are just selling you what befoure were the resource small settlements in the maps. You have been sold that Fantasy story about 183 regions.