I dont like exterior nest boxes that you raise the lid on. Alway disturbing a chicken getting ready to lay. Walking into the coop. Is less disturbing. Also I have had eggs freeze due to cold air blowing under the nest boxes.
My boxes have an outside access, but they are actually part of the footprint of the coop. Minimally invasive to sneak the door open for a quick peek. IMO, less invasive than walking into the coop to take a peek. Outside access next boxes are also extremely helpful for anyone who has asthma. Less exposure to bird dander. In 2 years, with outside access boxes, I've only lost 2 eggs to freezing, in my 44.6 lat. climate.
P.P. mentioned issues with cold winters. For those of us who live where the ground is frozen at least 5 months of the year, I consider that it's a necessity to have a "sun room" available for the flock. My sun room consists of a section of the run, with poly covering south, east and north walls of one bay of the run. This bay is partially covered with 2 x 4 wire, with the remainder covered with a green house tarp. There is a deep composting litter in this area. With winter temp of 15*, the birds would be out in their sun room all day long, dust bathing and turning the compost. It's well worth it for me to be knocking snow off that sun room roof, and shoveling a path from pop door to sun room during and after every storm.