Various reasons.
Bruder is a great trailer, but the purchase terms were, in my opinion, unreasonable. We also did not have the best of luck in our communication with Bruder during the order placing process. These issues led us to abandon the Bruder purchase.
ZoneRV- looks like a great trailer, but they are only offering their Expedition 10.0 and Expedition 12.0 to the US market. These are a little small for what we wanted. We were looking forward to viewing those models at Expo West 2020, but unfortunately, we all know how that went. Now if they would bring their Off-Road series here, that would be a great trailer for us and the US market. There is nothing like the Zone RV Off Road Series here in the US.
Oliver- Again, nice trailer, but not setup for off road. I don't think it would survive where we wanted to take it.
HQ-19 Honestly, this was not our first choice. In the end, we found it was the trailer that had the least number of compromises. My initial issues with the trailer was the fit and finish and I had severe reservations about the Chinese manufacture of parts. (first saw them at Overland Expo East 2019) Having owned ours now for 4 months, of which we have spent about 60 days/nights in the trailer, quality has not been an issue. All of the failures we've seen, all minor items, has been from the domestic sourced parts.
What's the lead time on getting your HQ-21?