As a side note: Rio Grande Electric Cooperative has the single longest transmission line in the US (As of 1995).
It was nicknamed 'Old Leaky'. If I remember correctly, it had line losses on the order of 15%. Rio Grande, to my knowledge, has never done well financially. I think the line has something to do with it. With the measurement of customers per mile of line, it was also awful - about .5 customer meters per mile. Most meters were lumped in a few small developments in the Big Bend Park.
None, except increased line loss and side effects like cost of maintenance. Line loss is a function of distance, AC vs DC, conductor types, coronal loss, voltage, etc. Line length(resistance / impedance) is the primary factor after AC/DC and voltage.
So, your question, as asked, makes little sense to me. Unless you are referring to impedance or resistance....
Since you refuse to consider line loss (impedance/resistance, etc), the answer is: no difference.