Support design depends on several factors.  These include appearance, economics, loads, height, track design, and soil conditions.  Each design has to trade off these factors. 
 
Appearance - the impression that you want to make.  Tubes look modern and streamline.  Lots of sticks make it look like a woodie. 
 
Economics - This includes the cost to fabricate, the cost to ship, the cost to erect, and the cost to maintain.  All sorts of trade offs can be made here that change the preferred design.  For example, big tubes take less labor to paint but little sticks can be galvanized so they don't need paint. 
 
Loads - Hurricane winds or earthquake loads can affect the selection. 
 
Height - Tubes tend to be good for shorter heights, but really big hills favor frames. 
 
Track design - How far the track can span between supports affects design.  Long spans favor tubes.  The very short spans of wood track favor sticks. 
 
Soil conditions affect spans that are used and as a result the structure.