With regards to the caddy - I bought one after getting my Warrior SE (the S200), and wouldn't be without it. I store my cleaner in a shed that is about 50 feet from the pool. When I had to use it, I hauled out the cleaner and it's long cord - not that heavy, but cumbersome to move - in one trip, then went back to get the power supply. I would then hook the cleaner cord to the power supply, plug it in, and run it. I had to disconnect the power supply from the Warrior SE each time as it was too bulky for me to carry the unit with everything connected.
With the caddy, the power supply is mounted on the caddy, and the long cord is stored on the handle. I just roll the entire unit to the pool, set the cleaner in, plug it in and start it. The cleaner cord is always connected to the power supply. When done, I lift the cleaner out and set it on the caddy, roll up the cord, then roll the entire unit into my shed. Makes the whole process so much easier!
After having no caddy for several months, then adding it and using it now for several months, I can easily say there is no way I would ever order another robot without a caddy. It just makes my life easier!
If you do get one, make sure you get the new version - the S200 power supply does not fit on the older version. New version is Dolphin 9996087-ASSY Carry Caddy (2015 & Newer). Old version is Dolphin 9996084-ASSY Universal Robotic Pool Caddy.