By my calculations, if their Bastila fallen has a speed of 309, then your Bastila fallen would need a speed of 305 if your Revan goes first and uses Force Storm.
If your Revan goes first at 328 speed, then an enemy Bastila at 309 would have her tm bar filled at 94.2%. Your Bastila at 305 would be filled at 93.0%.
This means that in order to fill up the rest of the turn meter bar, yours needs to travel 7%, while the enemy Bastila only needs to travel 5.8%. In order for your Bastila to make up that difference, her speed needs to be 375 in order to travel that distance faster, and if she started at 305 and got +75 from Ferocity, then she will be at 380 and can go before the enemy Bastila.
Conversely, if your Bastila is at 304 in the same scenario, her tm bar will only be 92.7% full, and in order to travel 7.3% in the time it takes the enemy to travel 5.8%, she needs to be 391 speed. Since 304+75 = 379, this scenario starting at 304 will make your Bastila go second.
Edit - For the purposes of this explanation, I rounded numbers to 2-3 digits. I actually put the numbers into Excel where it wasn't rounding, but was using full numbers.