I don't think I need an argument for the obvious.
Two exact spells: one cast in 1 round, one cast in 10 minutes. Which one allows for more creative uses?
This is the disconnect. It's not which spell allows for more creative uses, it's which spell allows for more creativity from the players. If
water breathing takes one round then any time someone is drowning or needs to go under water that's the thing to use. If on the other hand, it takes 10 minutes the players have to think of some other way to save the victim (like use that swim skill for example, or lower a pole in or, well, be creative).
water breathing stops being the default no-brainer option and just becomes an option to use, to be weighed by the time factor ("well we could use water breathing or we could risk the swim to the bottom without it, it's faster but has more risk").
You could argue that the swim skill has infinite uses while
water breathing is limited use, but really, how often is the DM going to pull the "save drowning victim" or "retrieve something under water" shtick per adventure?
In what situation could the 10 minute version be more creative than the 1 round version. Even if one says, "With the added time restraint, the 10 min version means that people have to be more creative to find it useful," I'd reply with, "The guy with the 1 round version can say 'I'm going to wait 9 minutes and 9 rounds before casting the spell so I'll be as exactly as creative as the longer cast variety in my using of the spell."
It's the gaming equivalent of "Anything you can do, I can do better. I can do anything better than you."
Again the 10 minute version promotes creativity by not being the default obvious option. As for "Anything you can do, I can do better. I can do anything better than you." - that's exactly why 3e mages can be irksome at mid levels and above.
The more utility something possesses, the greater probability it will be creatively used.
joe b.
But also the greater the probability it becomes the obvious default option thereby stifling actual player creativity.