Netgear unite explore 815S slow speeds

I just bought this mobile hotspot and although I'm getting better speeds than I get using my cell as a hotspot it still isn't anything to write home about. I live very rural and with AT&T cell service I run around 3-4 Mbps. Now with this hotspot I am getting around 7-9 Mbps. Side note: My husband's phone hotspot usually gets around 6-7 Mbps, I don't understand why but for 15 years even when we had the exact same phone his has always had better performance. My question is would upgrading to the Nighthawk M1000 make that much of a difference? Or should I invest in a booster? Extender? Router? I use to be able to understand all of this information better but due to now having MS it is very hard for me to understand the technicality of this. For this reason I ask for simple answers without the technical jargon please. Thanks