Express LRS has basically the longest range of any current RC link protocol. It was developed by and for FPV drone guys. The range at 100mw is insanely long somthing like 20km under ideal conditions and it can output up to 250mw. Some peoeple have gotte over 100km out of it at full power with a directional antenna. For line of site R/C I would leave it at the default 100mw and set it to "dynamic" where it adjusts output power to maintain the link.
I believe the Crossfire system still has the longer range, in real world terms, due to better penetration at 865mhz or 915mhz frequencies - simply down to the physics of the wave. It's still used for scientific purposes - as far as I know.
The other thing of course is that the full fat version can transmit upto 2000mW.
Obviously, this will far exceed what most FPV systems' video range is, but the fact remains.
Express LRS is open source and much cheaper and has a 900mhz option, so I suppose at that frequency the 2 are essentially the same thing - one open source, the other proprietary.
At 2.4ghz, the Express LRS has extremely low latency (5ms) and 1000hz refresh rate. Plus being open source, it's constantly being updated, where as the 'industry standard' Crossfire is more......sedatary.
The crossfire setup I have to say was fairly streamlined and slick to get up and running. I love the little OLED screen on the full module!

Whilst not difficult according to users, Express LRS definitely takes more time to get sorted. Joshua Bardwell is a huge fan, so it must be good!