Ride-a-long/carousel type changers save a lot of time with the machine not having to run to a fixed tool changer rack. They of course add complexity and moving parts, but they are much faster. In my experience what you will find is when you start knocking out sheets fast you start focusing on 10 seconds here, 15 seconds there, to go faster and faster.
There is no way either of those machines takes 8-10 hrs to run a 15 box job. Not possible unless the shop has some ridiculously ridiculous machining details or is running painfully conservatively. And there is no way you will ever have a man outrun the machine. If anything you could have your man cutting rectangular parts with no machining (shelves, decks, stretchers) on a saw while sheets are running on the CNC but more than likely there will be no time for that. He will be busy the entire time processing, loading, unloading, labeling, etc.
Your rapid numbers are definitely an indicator of the machines speed. As you say, your never going cut at those number but they indicate more speed. Every little move you can run faster is just faster.
That being said, in my opinion you have to evaluate what a realistic quantity of sheets per day you will run on average. I have a fixed position changer (rear, 10 tools), no drill block, and my average sheet on cabs is probably in the 6 minute range for standard cabs. Thats an average number between sheets with large parts and not a lot of drilling running in the 3-5 minute range, and some sheets with a lot of drilling and a lot of small parts running way up in the 8-11 minute range (those your wanting to gouge your eyeballs out).
But in the end at the six minute average, with probably half that to clear and re-load, you may as well say 7 sheets an hour, about 50 sheets a day.
I will personally in my business never have a need to run 50 sheets a day, 5 days a week and while the speed gain of a ride along carousel, multiple drill blocks, sweep, auto load/unload, would be heaven, I dont have the need or desire for growth to justify the investment in cash, real estate, etc.
In the end my input would be to quantify the type of work you intend to do with the machine, and try to forecast what your anticipated production quantity needed per hour/day/week is out of the machine.
In my experience with the fixed ATC the only thing I would wish for would be more than 10 tools (a second 10 tool rack would be nice) and possibly a drill block but honestly for my shop even the drill block is not something I miss having. The more tool want is because we do a lot of varied work not just cab sheets and it would be a luxury to have 20 tools chucked and ready at all times. If I were running my 50 sheets a day and still had more sitting back not getting run it would be completely different but I have only a hand full of times had a need to run 250 sheets a week and they werent cabinet jobs.
You really just need to establish your budget, your production need, and start battling it out from there in my opinion.