I believe it's just aesthetics. Whether you're an old 1930's style tower or a modern glass tower, they both give you 1836 people as a base. Both I think can be boosted the same way through the specialty buildings. Maybe there are some tax implications? Not sure.
Something I noticed a few days ago, a residential building can only have its population boosted a maximum of 100% for each specialty. I have a few Luxury Casinos that boost 60% each. I overlapped some of their areas of influence to create a super area of 120% boost. But, when I stuck a residential building in that area, the population boost I got was only 1836 people, 100% of that tower. Tried the same for Parks and Transportation.
I haven't had a residential building that isn't a glass tower for a long time now. If someone does have some older towers and has enough specialty buildings to repeat my test above, they should see if they are also capped at 100% or maybe something less.