There are many reasons that people like myself who live close to the Nooksack choose to spend most of their fishing time north of the border. Here are the top ones for me:
1. The tribal netting schedule - it is usually 6 days per week, and although you can find fish that sneak through, you have to really spend a lot of time to find where they are (or fish by the hatcheries where the fish get stale really quickly)
2. Visibility - the north fork of the Nooksack is fed by a glacier, and if weather is warm, there is a good chance you will have less than 1 foot of visibility. I have found 18 inches to be pretty good fishing, but less than that is really pushing it. The south fork runs clear but it is a small stream and opens later in the season, and no bait is allowed on the south fork.
3. Access - The C/V has amazing public access for it's entire length. The Nooksack, especially the main stem, has very limited public access, so if you don't have a jet sled or drift boat, it can be difficult to access any productive spots.
4. Fish size - Although the late season unclipped fish (probably not wild, the hatcheries don't clip all fish) can be quite large, most of the clipped coho are quite small, and as mentioned above, it is rumored that this is because only the small fish make it through the nets. Last season my only coho on the Nooksack was a 10 inch jack. Granted, I only tried one day for coho.
The one time I will get out on the Nooksack is for pinks, because they come in earlier than other runs and in good numbers. Actually, I think this is the earliest run south of and including the Fraser river. They generally open in mid July and good numbers can be found for the whole month of August. They are also on the small side like the coho - lots of 2 lb fish, but they are very fresh if you get them in the lower river.
The north fork is known for a good run of large chum in November, but I don't know that it is worth traveling for when chum are relatively plentiful everywhere.