1stly as joe ox said the big lamp will be seen first, when the rabbit senses that the dog is there it wont be bothered about its colour,
2ndly, the white dogs do stand out more on light nights, i have a white bitch and on light nights when your walking up to your quarry you can see the bitch where as the brindle dogs blend in more,
3rdly if your gonna be mooching about through the day in areas you shouldnt be obviously the white dog is gonna give the game away earlier,
my advise would be to let the pup pick you.. which ever is more forward or confident would be my choice, but if they are v