Originally Posted by Michel Gagnon
Now let me throw another consideration: cargo size and weight.
If my calculations are OK, the Yak has a 120-L bag and the 2-wheeled Burley Nomad has a 160-L capacity. Large panniers like Arkels touring series offer 54-L rear and 38-L front (GT series). for a total of 92 L... plus whatever you want to put on top of the rear rack. If one of you prefers to ride with panniers and the other one with a trailer, one solution might be to have one person carry the heavy and dense stuff in panniers (i.e. repair gear, food...) and the other one carry the light and blky stuff like clothing in a trailer.
FYI - I have carefully weighed and measured the latest black "anniversary edition" yak trailer. Although the yak sak's stated volume is sometimes listed as 7200 cubic inches, this is simply not possible (the same folks claim a weight of 13 lbs, HA!). I think someone took the sak's dimensions and calculated a volume (like a big, open bag), without considering that the rolltop closure design greatly reduces the bag volume as it is closed. I estimate the maximum volume of the yak sak to be ~ 4800 cubic inches, or ~80 liters. Which is slightly less than my 2 pairs of 42 liter panniers. Of course, you can stack stuff on top of panniers/rack or the yak sack. They provide about equal "stacking areas", but the yak would carry this weight about 1 foot lower.
Also, the yak trailer complete weighs 18 lbs (8 kg). My 2 panniers and 2 racks combined weigh 12 lbs (5.5 kg). Add a big handlebar bag (2.2 lbs/1 kg, 800 in3/13 L) and you still have a volume:weight advantage over the yak.