I can't compare against others but I can give you a single data point.
We rented a popup from Jack's last year to see if we wanted to move away from tent camping and to save ~1K towing miles vs. renting locally. We then proceeded to put over 2.5K miles on it staying in the Badlands and Custer before heading out to hit several national parks in Wyoming, Montana, Utah, and Colorado.
The company was easy to work with when reserving, though the pickup process was a bit convoluted as the main rental guy was out of the office on the pick-up day and the fill-in read the reservations wrong so he gave us the wrong unit (same model) which had not been fully prepped prior to our arrival. When we returned it we heard "Oh, we've been looking for that one for weeks".
Overall it was a positive experience and I would consider them again in the future.