It makes absolutely no difference. To illustrate why, let's break down the individual changes in direction by 90° segments through the trap, beginning with the vertical drop out the tailpiece:
- To horizontal
- To vertical (upward)
- To horizontal
- Through any horizontal bends to the tee
None of this changes when you swing the trap pivots. It's always exactly the same sequence. While a fluid dynamics geek could argue the finer points of the forces involved, the variation is negligible.