I have owned the 875r for about 10 years now and I like it a lot, but saw a pretty good deal on the NTG5 and decided to add it to my small (2 shotguns, 1 very cheap cardioid and 4 lavalieres) collection.

I put both microphones 8 cm away in parallel with the front of their interference tube at the same height. I spoke a bit and used my phone to generate white noise (which I understand by the nature of the crappy speaker on a phone will be not anywhere close to real white noise, plus there is a lot of noise in London which overlaps with my test) and placed it around the microphones using a measuring tape to keep the distances where I wanted them. The recorder was my also 10 year old Tascam DR-680 which has pretty decent preamps in my experience and both channels were set to the same gain.

The main takeaways:

The NTG-5 is noticeably hotter. The NTG-5 rejects way more noise to the sides. The AT-875r has a low cut that works great (I actually like my voice better with the unprocessed AT-875r)

You can download the file here if you want to hear it yourself.  

https://drive.google.com/file/d/1eatefYMnykOYERRRcEC8GuBPbhL3W32i/view?usp=sharing