I recommend go for whichever you find the most aesthetically appealing. The selection on any particular flight is limited, and the monetary value of the houses you will be offered is trivial, as Mike Turnbull has already pointed out.

Although these houses are collectible, it is surely a niche market. My guess is that they only truly appeal to a subset of aviation nuts, frequent KLM longhaul J class flyers, and KLM employees who can get their hands on them easily. For some, only houses collected the hard way (i.e. bum-in-seat or possibly trading duplicates with another such bum) count, every other methods is considered unsporting. The ultimate goal is of course a complete collection.

Johan