First Id consider whether it is going to be housed in garage and will it fit? If you want one that you can stand in, likely, it will be to tall for standard 7ft garage entry.
I have a 6x10 enclosed. If the reels are going out there side door and machines in the back you will be hard pressed fitting a 250 gallon tote in there.
Make sure you get one with the air vents built into the sides. Also make sure you coat with a Thompson water seal all around. Amazing how fast that plywood will tear up. I was looking into enclosed for safety but couldn’t pull the trigger on the price just yet.