I have both these devices. Even if we ignore the price, I'd say that the choice should be self-evident based on your use case. The modem is pretty much the only common feature.
If you want an ordinary WiFi router for indoor use, with an internal 4G modem for primary or backup WAN, then the MF286D is the perfect choice. If you already have the indoor WiFi router and want to connect it to a 4G/5G modem with antennas mounted outdoors for optimal signal, then consider the NR7101.
I say "consider" because we obviously can't ignore the price. Both devices are available second hand around here, but the price still favours the MF286D by a factor of 5 or so. And more importantly, they are all operator branded and the lock down of the NR7101 has been improved since I wrote the instructions in the wiki. Connecting a console to the MF286D is slightly more difficult (no header installed and clips holding the case together), but it will always allow OpenWrt installation. Second hand operator branded NR7101s are more risky. Some of them might be unusuable with the current public knowledge. And that's for the price of 5 MF286Ds..
If you want an ordinary WiFi router for indoor use, with an internal 4G modem for primary or backup WAN, then the MF286D is the perfect choice. If you already have the indoor WiFi router and want to connect it to a 4G/5G modem with antennas mounted outdoors for optimal signal, then consider the NR7101.
In the second situation, please also consider plugging a Huawei E3372 into a USB port of your existing router. It would be much cheaper while still allowing external antennas.
If you get the E3372h variant of the modem you have the following options:
Use it as it is: it will be visible as an Ethernet card, function as a NAT router with quite low number of supported concurrent TCP flows, but will also handle reconnections without any OpenWrt specific bugs.
Reflash it to the stick (21.x) firmware using balong-flash: the modem will speak NCM then. You get rid of one NAT layer this way and potentially get a public IP if your network provider offers it. The lack of NAT on the modem also reduces the attack surface - note that the modem is running a 12+ years old unpatched kernel, so it can matter. But then the OpenWrt-specific lack of the reconnection feature will bite you.
External antenna and outdoor antenna is not the same. Outdoor antennas will be expensive either way, and rather complicated with the MIMO modems we're talking about here.
The reason you should consider NR7101 or similar devices if you need an outdoor antenna is because it simplifies cabling. Long antenna cables are bad, expensive, and hard to work with. Mounting the modem closer to the antenna is much better in every way. And it makes it possible to mount more than 2 of the antennas outdoors (all of them in fact). I don't think that's practical otherwise.
You might use something like the Poynting ePoynt series to overcome the antenna cabling problem:
But it's not necessarily cheaper. And you still lose some of the NR7101 features like the antenna ground plane serving as a cooling device for router and modem.
FWIW, I do have an E3372 and a few other USB stick modems too. Never considered using those But I have been using an EM7565 in a USB adapter. It's obviously as good as the internal modem in the MF286D (same Qualcomm chipset). But I prefer the internal modem mounting for practical and esthetical reasons.
Yes, not in the TOH (yet?)
Yes, runs OpenWRT (currently 21.02)
Yes, has some non-std componets and features
Yes, runs out of the box for the stated application
No, probaly not for tinkering
I only offer it for the OP to be aware of and expect he\she will do their homework.
ToH isn't 100% accurate, one need to search the git commits.
99% of all routers run openwrt or LEDE, even the ones never getting supported.
"it runs openwrt, therefore it can be supported", is flawled logic, even if those two probably will be, down the road.
But it's quite possible that's an optional component you have to order specifically. The mini-PCIe slot conflicts with the PoE module so mounting both makes no sense for example.
