I've always preferred the look of the 88 over the 188, but this is just personal taste.
With some other land-to-seaplane conversions, I believe earlier versions were typically used, at least in the prototype stage. This freed the more up-to-date models for front-line duties (remembering the Spitfire seaplane).
Whichever you decide, I think the results will be fantastic!
Brian da Basher