Well, My opinion... I would pick the FiST. but...
Are you using it for a daily and that's it? any future mods? any track days/autocross? only a highway car? Are you wanting a more comfortable ride or better gas mileage? All of these lead to one or the other. if it were me I'd choose these in an order that is most important to you to the least important. and find the one that gives you the most of it.
For more comfort, no track days, mostly highway. I'd choose the FoST.
for something you want to do an occasional track day, mod, and get great gas mileage on the highway, I'd pick the FiST.
These are my opinions though. what appeals to you the most is what you should do. The Only reason I would choose a FoST over a FiST is because I would NEED the space difference. which I do not forsee me needing.