I have sorted these pretty close to my priority sequence. I am more willing to compromise the further down the list I go.
Size: I am nominally a Large. But I have ruled out one brand because the Large was too short and the next size up was too tall. I ruled out another because the Large was too long and not tall enough. The size either size failed for similar reasons. So if I cannot ride one, I have to see the geometry table.
Full suss: There is no way that I would survive on a hardtail!
A mullet: 29" front, 27.5" rear (to stop my arse from being buzzed when I am descending).
Weight: 24kg or less.
One brand of Electrics: I want the motor, battery, charger, display, mode shifter, wiring, software all to be under one brand name. One place to go to when problems occur.
Battery: 625 wh-rs minimum. OK, 600 at a push, but no lower.
Motor: Full fat. Shimano for preference because I love the way they ride. I know Shimano get a lot of bad press on here, but my experience has been flawless. Bosch in second place.
Charger: 4-amp minimum. Life is too short to wait for the battery to charge.
Suspension travel: 160F / 150-160 R
Reviews: 5 star. There are so many bikes that there is bound to be one you like that gets a 5* review. I would compromise to 4* but absolutely no lower.
Frame: Carbon fibre. Has to be really, to meet the weight requirement.
Suspension Design: Horst link or very near facsimile.
Suspension spec: Fox or Rockshox. Has to be top of the range or close to it or I'll spend loads of money on upgrades.
Transmission: 12-speed for preference, will take 10-speed if the spread of gears is there. Shimano for preference. Sram a very close second.
Braking: 200mm dia discs. Shimano for preference. Sram a very close second.
Rims: Alloy, not carbon fibre. 30mm minimum internal rim width.
Tyres: If they are not grippy, then that's an up-front cost for me to change them. Any colour as long as it's black (logos excepted).
Colour: Not shit! I've had dark red/white, bright blue/white, light green, shiny black, satin black, metallic blue

love

, gloss red/satin black. They were all lovely, but I have seen some shocking colours on the media. Pastels, shades of brown, cafe au lait, any swirly pattern in any colour. I know shit when I see it.
Look back factor: It has to float my boat, or else why would I want to rides it. When I walk away, do I look back at it?