Excepting the adjustable Showas on Monsters, ST´s etc., adjustable suspension tends to have slightly better function overall; at least they lend themselves better for modifications aimed at tailoring for your personal needs. Of course, once you´ve found a setting you like you won´t fiddle much with the adjusters, but at least you have a little more possibility to find a setting you like.
For springs, I have found very few options for the showas with the correct length. I use the 245 mm Öhlins springs fo the R&T43 forks, available in 0.5 N/mm steps from 7N/mm to 11N/mm if memory serves. To make up for the missing length, I use alu tubing 38 mm Outer Ø, 1.5 or 2.0 mm wall thickness, and the spring support washers used in most SBK forks.
I don´t have the Öhlins part numbers right now, can get them if you´re interested.
20170209_200528 by
torbjörn bergström, on Flickr