Over the years I have been kayaking down in the Borja and Tena area at least 4 times. This was in the early years of Small World and the DeRiemers setting up their businesses. Both are very high quality and great folks to boat with. The deal with either one of these outfitters is they have every thing dialed in perfectly. All you do is boat every day on a quality run. They have the gear, the drivers, know the rivers, have the facilities and take care of you to make the most of a boating vacation in a foreign country.
I have run into private boaters down there several times. Each time the private boaters were asking the outfitters all sorts of questions - all of which were answered. The issues are lack of quality Spanish speaking skills means it takes time to do every thing - granted a lot of locals are now able to speak some English and it can be done by less than perfect knowledge of Spanish. Knowing where to stay and eat is also something to figure out. The outfitters know where to eat and sleep and I have never been in a less than quality food and board place. Some were and are superior.
I wish I had the skill set to go down there and do private trips but unless you have lots of time and are very adventurous on where you eat, sleep or drive with - both Small World and the DeRiemers earn their pay.
Admiration from me for those folks who can travel in foreign countries on their own, I am one who is hesitant to do that. I just cut down on expenses till I saved up the money to use the outfitters.