I wouldn't say 4.05 is a far cry. If you're taking action when it's 4.9, then maybe reconsider what ulns is. Imo, anything less than 4 is a problem as it gets into a danger zone where it could bottom out quickly. I keep my nitrate less than 10 and over 4. Your corals aren't going to look drastically different if you keep it in that range. Nitrate doesn't need to be held within the same +/- 0.5 range like alkalinity does. It's the lack of nitrate that causes nearly immediate problems/death. If you're running a ulns tank, then you're almost never worried about getting over 10 as you're probably dosing nitrates already.If your under 5ppm nd you don't mind the process, I would use the LR kit. Little more accurate at lower ranges as you can see by your comparison. 4.05 is a far cry from 4.9. Thats nearly a 1ppm difference.
For me, the high range test is better as it's as simple as it gets and as accurate as you'll need it to be. Remember, we were dealing with wildly inaccurate readings prior to the LR and HR Hanna Checkers. Our reefs did fine before now, with the exception of tanks where tests were inaccurate and people had no nitrates. When I had done my last red sea nitrate test on my 40 breeder prior to getting the Hanna hr checker, it said my nitrate was in the range of 16-25. When I got this test, it let me know that I actually had very little nitrates. Nitrates then bottomed out and I started seeing dinos, so I now dose neonitro to maintain my levels. Dinos are completely gone and coraline growth is exploding now. Our tanks are going to excel more now imo. This is a big step for reefing. I believe we'll look back at these testers as a mile marker for stability in our tanks.