The tips are just a facade, but the pipes leading to the tips have a real function. Come on Borla!
Don't know how much the downward pipes impact the sound, but I see a big difference from the Sport to the ST, especially for only 35 more HP. I found the below on an Internet page about tuning exhaust systems.
"Down-turned tips, particularly those that force the exhaust underneath the car, can deepen the exhaust note by bouncing sound off the ground and using the undercarriage as a resonator. The ground will absorb much of the annoying high-frequency sound from smaller displacement or more restricted engines."
EXHAUST TIPS AND TONE
Whether exhaust tips alone can change the sound of a car depends largely on the other components used. Going from a 1.75-inch diameter tip and pipe to a 3-inch tip can make the exhaust note much deeper but still less so than simply buying a new flow through muffler (and low restiction cat).. There are a number of factors to take into consideration, such as intended effects, budget and additional modifications.
Factors
1. Though the main part of the exhaust note is determined by the silencers, resonators, catalytic converters and the pipe diameter, there are a few factors that affect sound at the tip. Tip size actually has very little to do with sound, unless you go to a notably larger or smaller diameter. Other component choices and how restrictive they are is key. Smaller diameter tips will additionally restrict the engine, slowing the exhaust stream and decreasing engine noise. A larger diameter tip will make the engine louder only if the original tip was a restriction.
Down-turned tips, particularly those that force the exhaust underneath the car, can deepen the exhaust note by bouncing sound off the ground and using the undercarriage as a resonator. The ground will absorb much of the annoying high-frequency sound from smaller displacement or more restricted engines.
Ah ........ Such is life. 
