There are quite a few strings attached regarding SF's free tech.
You may or may not find a free satellite, you may not yet have the prerequisite techs you need for your free tech of choice, you may have to go down the eccology path without need for miasmic repulsors (and build one without need), the waiting satellite may block the production of civilian units....
FI's may come a bit later, but you can time it much easier. You might be able to rush to tier 3 even, or tier 2 leaf techs for a massive affinity boost and tier 3 units. And you'll get a free tech soon afterwards (maybe even at 15 virtues from the synergy bonus as someone said already).
Overall, SF will usually get it's free tech earlier, but FI will often get far more benefit from free techs overall practically without opportunity cost. Which is good, because the SF has another bonus regarding orbital units, FI not.
I'm even inclined to say that FI's free techs are so strong that they easily beat SF's combined bonus. Many orbital units don't profit from staying up there longer at all (miasmic repulsor/condenser, probably climate control) and for many others the time bonus is nonessential.