While I've never mounted them in same vehicle, we had a Dominator 8 in our department's Tahoe. It was great with the hatch open, but through the tint it was nearly non-existent. I have the XL6 Commander (Dual Color) in my Explorer, also with factory tint. While it does loose some kick through the tint, it is still much brighter than the Dominator. And I've always been a Whelen fan.
hahahah pimp, ill be completely honest with you, i saw that video on youtube just after strobesnmore posted it, and i almost took my post down, im definitely going with the E66, i have a D6 dash light and they are crazy bright lights!