The 2 PT lines have the same basic construction.
The differences are, the Tracer has similar floorplans but is a few feet shorter, has less windows, less cabinets, different slide mechanisms and I'm sure there are a couple of other things that I can't think of right now.
So the Tracer is lighter and cost less than the LaCrosse. It all depends on your brother's needs and what he is willing to pay for one.
Either way he'll be getting a great trailer and free membership as a PT Crew Member!