In my experience and setup, the difference may be up to around 10 Mbps, and B618 is not always better than M1.
As some of the forumers pointed out, M1 may get heated up relatively more easier as compared with B618.
Since you are using it for 24/7/365, B618 may be a better choice here.
Hope this will be helpful.
Thanks.

Good morning.
A few things can be considered
(1) Mobile router: Netgear Nighthawk M1
(2) Fixed router: Huawei B618
(3) 4G antenna
It is always safer if you can borrow this (these) item(s) from any friend to try out first before deciding on purchase (if possible) so that you will know what to expect if you really have made up your decision.
If you travel oftenly and need the internet with you, please consider (1) as it has its own rechargeable battery.
If you are using this I150 exclusively at home, then please consider (2) or (1).
Item (3) is optional as the improvement seen is variable.
Thanks and hope this will help you.
Have a good day.

May consider band locking and see if speed improves.

Post paid 150 /2021
Hotpot is unlimited until fup of 1TB
I think hot-spot is limited to 3 users
Speed cap at 10Mbps equivalent to 1.25 MB per sec if u r downloading files.