I don't do much landscape or hiking, but I often shoot cityscape, rivers and bridges at sunrise/sunset as I do a lot of city travel. I never really invested a lot in filters in the past.
Up until now, I've been fine with using 77mm circular filters (a cheapo CPL, B+W 10 stop, and a 3 stop ND). Most of my travel gear fits 77mm (Canon 16-35mm mk I, 24-70 mk I, and 85mm MK II with a 77mm to 72mm adapter). I've been doing grads in lightroom up until now.
So I forsee the day coming that I'll be using 82mm down the road (since the 16-35MM mk II and the 24-70 Mk II are both 82mm), and looking to buy square filters now.
I was thinking of the following:
Formatt Hitech Aluminum Holder
77mm + 82mm adapter ring
Lee Resin 4x6" .06 Hard Grad
Lee Resin 4x6" .09 Soft Grad
Format Hitech 4x6" Resin .09 Reverse Grad
Lee Resin 4x4"0.9 ND
Format Hitech Firecrest 4x4" 10 ND
And sometime down the road, add a (relatively) cheap 105mm CPL like the Sigma.
My thinking is that the firecrest price premium counts most on long exposure (the ND), and it seems to be getting a lot of supporters over the lee big stopper. For city, the .06 hard and the .09 reverse grad would be useful for distant horizons near sunrise/sunset, and the .09 soft would be useful for close horizons.
Is this sound reasoning? Since the dollar amount is so large, I wanted a voice of reason before I threw my money in.