I like the large format idea. I went with two 3L instead of one 5L. Easier to store and handle, while maintaining festivity.
My life experience with the really large formats is that its much harder to actually find the events to open them at, rather than just having magnums or a case of 750mls. I do grant the bottles can look neat, while being stored, and even afterwards.
For an imperial purchased, and poured at a party, I had everyone sign the bottle with paint pens and still have it in my garage.