Jam,
First off congrats on the restaurant soon to open! As for your question here are some thoughts.
Space: Depending on your space, one 250 may fit better, or vise versa.
Cooking: Having more than one cooker is always nice if you like to cook things all at the same time but at different temps. For instance 275 for ribs and 235 for pork etc. Or, while one is fired up for Q, the other can be cold smoking salmon, cheese, charcuterie etc.
It really all depends on what/how you plan to cook things. Neither is a bad choice! one more thing.....Unless you plan to be cooking 24/7 in which case this wouldn't matter- if you are in a slow period or have a party to cook for with specific needs, the 250 may be too big for your needs. But since you will have two of them, if you get busy and require more space, then you have another option with the second cooker.
Good luck and happy Q'en
phillip