I liked the latest CTT article on AIUs. Apparently, AIUs are nothing more than relays, which is a fancy word for “switches that control other switches.”
However, the advantage of AIUs is that you can program/interface the AIU with the TIU and have all controls in one hand, or even program everything to work automatically in whatever time and sequence you choose. The possibilities are endless.
I don’t plan (for now) to acquire an AIU, as my next layout will be rather smallish 4X8 with all controls within easy reach. Actually, I’m planning a 3-deck 4X8.