Hey Seb your OVER-thinking this.
If you want to improve your open water swim as well to your overall triathlon performance.
You have to cover all bases!
Most AG look for a "magic" set - while its really about the right *MIX*.
Fast w/ lots of rest - Fast w/ short rest - long steady continuous - progressive - ect.
Then depending on your skill/pedigree/mentality.
You then focus more on one or another