With my recent 5Ds R acquisition, the suitability of my lens selection came into question. Canon published a list of recommended lenses for the 5Ds R, with some of my L lenses notably missing from the list. As a result, I just acquired a Canon EF 35mm f/2 USM IS.
The new 35L II was really tempting me, but some painful trading would have been necessary, probably two nice lenses sacrificed, minimum. I decided 35mm is not sufficiently important to my shooting to justify that level of sacrifice; I tend to like to shoot either wider or longer than 35mm. Plus, my on-line pixel-peeping, and such, indicated that the 35L II, while more than thrice the price, was not three times better, optically; more like incrementally better, and in some flare-inducing conditions, it seems the 35 IS fares better than the 35L II. I find myself dealing with flare quite often.
It remains to be seen whether I will sell my 35L, now that I have the 35 IS. I really like the 35L on cropped-frame cameras, where its lesser edge and corner performance is nullified, and its wider aperture is of increased importance. People do not seem to fault the 35L's center performance; I certainly do not. The 35L on a crop body, such as a 7D Mark II, and 35 IS on my 5Ds R, may well complement each other nicely.
Notably, a "wild card" in the equation was my consideration of a Nikkor AF-S 35mm f/1.4G lens. I shoot with 12MP D700 and D3s cameras, too. The D3s, in particular, is a better night-shooting camera than a 5Ds R.
Parts of this were copied and pasted from a reply in another section of this forum.
Canon 5Ds R/7D2/7D/5D/40D/1D2N/M3; Nikon F6/D3s/D700/FM3A/1Dx/Coolpix A. Lens selection undergoing changes; some favorites: Zeiss 2/135 APO Sonnar, Canon 100mm f/2.8L Macro IS and 135L, Nikkor 14-24/2.8G and 24-70/2.8G.