When I'm ASMing, I choose to make my book like the PSMs, even if I'm not comfortable with the set up at first. Primarily, this is because I'm always up for new ideas. I don't want to get stagnant and set in my ways; I think you have to be highly flexible in this job. And so, a book that might look confusing to me at first could easily become my preferred method for a particular theatre genre. For example, the way you arrange a book for a musical (room for the score, blocking large chorus scenes, gigantic scene shifts, large numbers of cues) is/can be entirely different from a new play (with new pages added often, cuts, etc).
When I'm SMing, I let my ASMs decide what makes them most comfortable. It's easier if the book looks the same, but so long as it's the same pagination, I don't care. Plus, you might learn something from looking at their books. The duties of ASMs and SMs vary. When I ASM for example, I write all the props that should be onstage at the top of the script, because I'm the one that has to preset them and track their movments. It seems easier to me to just glance at the top of the page for what's coming up, especially when there are a LOT of props (Thank you, Plaid Tidings). But when I SM, I'm happy to just look at a plot and my notes. I'm not the one getting up from the table to handoff a prop, usually.