Well the boot LEDs (16LED) I ordered were not 42mm as advertised, thought I'd try them out in the vanity lights just to see in person how they fared facing towards the visor and towards the passenger.
39mm 16LED passenger side, facing towards passenger / Standard bulb driver side.
39mm 16LED passenger side facing towards passenger / 39mm 9LED driver side facing towards driver.
I sat in the passenger side and found that the 16LED facing the passenger illuminated the face much better, sitting in the drivers side I wasn't too bothered by the brightness of the passenger side light. I will see if it is too bright for me during actual night time driving.
I ended up leaving the 16led in the passenger side facing the passenger, 9led in the driver side facing the visor.