Blogger [radioforeveryone] set out to look at 19 different RTL-SDR dongles for use in receiving ADS-B (that’s the system where airplanes determine their position and broadcast it). Not all of the 19 worked, but you can read the detailed review of the 14 that did.
Granted, you might not want to pick up ADS-B, but the relative performance of these inexpensive devices is still interesting. The tests used Raspberry PI 3s and a consistent antenna and preamp system. Since ADS-B is frequently sent, the tests were at least 20 hours in length. The only caveat: the tests were only done two at a time, so it is not fair to directly compare total results across days.
The author points out that differences under about 2% don’t mean much. However, the article does draw a series of conclusions at the end. For instance, you can buy an $8 dongle and build a coketenna and have less than $10 tied up. You could also spend $150, but you won’t get 15 times the data nor 15 times the enjoyment. There is also quite a bit of info about heat dissipation, antennas, and other factors that will come into play no matter how you use the dongles.