The Pimax 4K BE is not a real 4K panel, it has a 2880x1440 OLED panel , same as the WMR headsets, that's why the resolution looks the same , don't know what panel brand Pimax uses in it but it should probably comparable to the Samsung Odyssey.
Choosing an headset today is like betting to the lottery , personally I'm pretty satisfied with the Lenovo Explorer, there are not big issues with it and works well with most ot VR titles, but of course there is room for improvement, but talking about VR...there will always be...
Vive Pro has the worst price tag, in my opinion totally unjustified, but if you already have the Steam controllers and base station it plays strongly in its favor....except you can wait for the Pimax 8K/5K to come out.
After having seen many Samsung Odyssey reviews I'm pretty convinced it is the best and cheapest solution, considering it uses the same exact OLED panel of the Vive Pro, but it has the disavantage of the weight, something to keep in consideration if you don't like the feeling, since it is not the lightest headset around (but the Vive Pro neither is...).
Until the perfect headset comes out, it is clearly a personal choice, and choosing wich factors are most important to you and wich ones you can leave out and get over