Can you tell us on the fence, how it is better? I'm seeing no internal weather measurements and no lifetime warranty
It uses the common Applied Ballistics as opposed to Geoballistics. Not a dealbreaker for me but I prefer AB.
No it doesn't have internal weather meters but with the Impact you can't turn them off including the compass. So if you go from a warm environment to a cold or change direction or it may not be giving you the solution you want. I really did not care for the compass feature.
The screen is much much easier to read especially in low light or bright light and works way better in the cold. It doesn't turn gray/black. The Impact sometimes updates the range but takes a second to update the firing solution so you might have 300-1.2, rerangr and it flashes 350-1.2 then finally 350-1.6. You can easily misread it and use the first set of numbers.
The batteries last much longer. It's not even comparable. It also has a battery life indicator while the Impact just tells you when they are about to die. Battery cover is easier to use.
The auto shutoff options are up to 15 minutes instead of the 3 minutes with the Impact. So in addition to eating batteries you usually have to leave the Vortex on so it doesn't shut off mid stage or mid stalk and then remember to turn it off.
The remote is wired so it won't go missing and doesn't require a Bluetooth connection which can disconnect and require several seconds to power on and reconnect. Also means it uses one battery not two. The only drawback to the whole unit is the remote plug connector is a weak point so you have to be careful.
You can turn the Fire4000 on with the remote so you only need to ever press one button. Gives vibratory feedback when ranging which is nice.
The buttons are much larger and easier to press. The Impact you have to press the ranging button so hard you can move your rifle and the most important button, the power/range button, is the smallest and hardest to press. The Fire4000 buttons are actually slightly raised so you can even find them with thin gloves on.
The visible laser used for zeroing can be turned on without tools and on my unit was much more accurately collimated. The Impact was way off and required you to find buildings and telephone poles to actually zero it.
Those are a few things that stuck out to me. Your needs/requirements may be different.
