I guess it's just a matter of what you carry in the way of lenses. If you use:
23mm Rod, best image case needs CF even with BSI sensor. 95mm Filter thread
28mm Rod, best image case needs CF even with BSI sensor. 95mm Filter thread
32mm Rod , best image, especially if shifted needs CF even with BSI sensor 105mm Filter Thread
35mm Blue Ring Schneider. 105mm Filter Thread
40-80 Blue Ring Schneider. 105mm Fliter Thread
75-150 Blue Ring Schnieder. 95mm or 86mm Filter thread, I can't remember off hand
14-24mm Nikon. curved outer element no filters
15mm Pentax curved outer element no filters
19mm Nikon curved outer element no filters
(net any wide 35mm camera lens with an outer element that is curved, as most are, which eliminates use of screw in filters).
All of these give you two options, at least from what I have found.
150mm Filter, in a sliding style holder, Lee, Wine Country, Nisi, etc. or 105mm filters, stacked.(if you are working with water an attempting to slow exposure or looking for a special effects style shot)
The 105mm screw in filters, I have used, however they are IMO a pain to use as you are constantly screwing and un screwing them, they are thin by design to allow stacking, fragile and just get to be problematic in the field, especially if you are needing a CL-PL and at least one ND. If you want a graduated ND, really not easy to do, you can emulate the effect by holding a ND over the lens and then slowly pulling it away. but not that easy at least for me.
With water, a CL-PL is pretty much a given need and if you shoot greens or fall foliage in bright light a CL-PL will make a huge difference as it will take the glare off the leaves and give a much more please look to the image.
What I moved to was the 150mm Wine Country filter system for Phase One, as I am going to be either carrying a 32mm Rodenstock, and will most likely use the CF (even if you don't the filter size is 86mm on the lens). Wine Country I believe was the first system to allow the CL-PL to stay in the system all the time, and allows you to rotate the CL-PL without having to rotate the entire filter system (like Lee). Wine Country takes any of the 150mm x 150mm filter from all the current companies, (I use the Nisi , Breakthrough Tech, Firecrest mainly), the holders snap into place and the entire setup locks into place on the lens. I rarely use a ND grad for the same reasons already pointed out, but often use the CL-PL and ND 6 or ND 10 depending on the scene.
I work in windy conditions a lot and personally have never noticed the 150mm filters in Wine Country being a sail, but I am using a massive XF and 35mm BL or Arca rm3di and 32mm Rodenstock, both of which are quite heavy IMO.
I fully agree the 150mm x 150mm filters are heavy and bulky, but there really is no other choice out there for lenses with such large outer elements.
One 150mm system by Wine Country fits: all my Phase lenses, my 14-24mm, Nikkor, my 15-35mm Pentax, my 32mm Rodenstock (I worry a bit about the weight of system on the front of of the 32mm as they by design are fragile and prone to misalignment due to so much mass in front of a simple copal shutter and the AU mount is odds are where I will eventually go with my 32mm).
What sold me on the Wine Country system was the integrated, geared CL-PL, since I use a CL-PL almost 100% of the time, it just works out easier for me. System is so simple to place on. Screw on the 105mm adapter ring, mount system, and you can leave the 105mm adapter ring on the lens in the bag by making a simple cover for the 105mm adapter plate.
Paul