If quality is your goal, look at New Horizon, Excel by Peterson and DVR. All three are, in the opinion of most well informed people better then either of the two you list.
All, are, much, much more expensive
Of the two you list, Arctic Fox would (and has been) my choice. Starting with the frame, the Lippert has a reputation of spotty quality, while the Northwoods has a solid rep. Search you will find complaints about Lippert frames in just about every forum on the 'net (except maybe those company owned ones where complaints about their rigs are deleted). I have never seen a complaint about a Northwoods frame failing, and Northwood refusing to setup up and fix all the problems (point of reference, I've been doing RV stuff on the Net for about 20 years).
This is our 2nd Northwoods (the first was 12 years old when we traded it in).