just got out of Kotz and there people looked to be getting some good bulls. talked with a few that went up with them and the couple seemed pretty satisfied. After my trip, I went over there to get a card from them. www.northernairtrophy.org I can tell you one thing, when we all showed up at the airport, Northern Air was the first one there to pick up their hunters. I will consider them as I was not to successfull with my hunt.
Northern Air Trophy is a guide service. As such, they can offer a larger variety of services than the transporters. I suspect you'll pay a higher price for some of the services, but you'll probably get more for your money.
The Western Arctic herd rarely seems to migrate like it did years ago. They are more spread out and migrate later. The area bio for where I live just returned from Onion portage below Ambler and said the migration thru there was spotty. Most of the herd is stiul north of the Brooks range.
I think a guide service like Northern Air, may be in a better position to offer successful hunts, then just a transporter. I think picking a spot for a successful bou hunt in unit 23 just isn't as easy as it used to be.