I know nothing about the Koala or Tracer, but we are on our second Funfinder. We are satisfied with our trailer and really like the quality of materials and appliances. However, the quality of workmanship could be better.
We were plagued by leaks on the first trailer, mostly from a lack of sealant from the factory. One that was especially hard to find was a leak in the bathroom, which we assumed was from the toilet. Finally discovered that the mount bolts for the spare tire bracket had absolutely no sealant around them at all. As soon as I got the second trailer home, I spent half a day checking and resealing every opening. (Found the same problem with spare tire bracket and corrected it before it became a problem.)
Other than leaks, I have had to replace some minor cabinet hardware and the panels in the cabinet doors eventually worked loose. The staples holding them in were too short and the door frames weren't thick enough for longer staples. I wound up making some wood splines to hold the panels in place.
If I had it to do over, I would probably buy a Funfinder again.
2010 Sierra 1500 Crew Cab
2009 Funfinder X 210WBS