The I box is supposed to be the 'easiest' way to make box joints. The incremental positioning fences like the LS have a lot more capability, but can be more complicated to use.
It depends on your planned projects. I use the old Router Workshop spacer fence system for box joints; quick and easy. I have an original Incra jig, but it rarely sees the light of day
https://www.routerworkshop.com/boxjoints.html
If you want to see some intricate box joint jigs......
https://m.youtube.com/watch?time_co...ubJJCU6Jocb4odT-zFt2-pajjLosPv8NdkZ0_0HOKVGKg
It depends on your planned projects. I use the old Router Workshop spacer fence system for box joints; quick and easy. I have an original Incra jig, but it rarely sees the light of day
https://www.routerworkshop.com/boxjoints.html
If you want to see some intricate box joint jigs......
https://m.youtube.com/watch?time_co...ubJJCU6Jocb4odT-zFt2-pajjLosPv8NdkZ0_0HOKVGKg