I've taken LFI-1 and LFI-2. I agree with mib2000 that if you can only take one, LFI-1 is an excellent choice.
That said, next year I'll probably look for more of a shooting academy. While I learned a lot at LFI-2, my shooting did not improve as much as I wanted, particularly while under stress.
LFI-2 spends a lot of time on handgun retention, which is taught using the Lindell system. One downside of the Lindell system is that it has many techniques and is prescriptive (e.g., you have to diagnose the attack and use the correct technique for that attack). This weekend, I'm taking a retention class using the Hamilton/Insights system. The Hamilton system is supposedly less prescriptive (fewer techniques). It is also destructive, which can be either an advantage or disadvantage, depending upon the circumstances.