I then purchased a TRENDnet USB 3.0 Gigabit adapter from Amazon to test on my Pi.

I've tested the onboard LAN port (rated as 10/100 Fast Ethernet, and driven through the onboard USB 2.0 bus), and a few different 802.11n WiFi cards, and the raw throughput speeds ranged from ~45 Mbps with the 802.11n cards (with a very strong signal) to ~94 Mbps with the onboard LAN. If you're taxing the CPU and USB device bandwidth on the new USB 3.0 ports, you might not get consistent Gbps-range performance, but in my testing so far, the Pi 4 can sustain over 900 Mbps (// I received a shipment of some Raspberry Pi 2 model B computers for a project I'm working on (more on that to come!), and as part of my project, I've been performing a ton of benchmarks on every aspect of the 2, B+, and A+ Pis I have on hand-CPU, disk (microSD), external SSD, external HDD, memory, and networking. Note about model 4: The Raspberry Pi 4 model B finally has true Gigabit wired LAN, owing to it's new I/O architecture. So if you have a 3 B+, there's no need to buy an external USB Gigabit adapter if you want to max out the wired networking speed! Note about model 3 B+: The Raspberry Pi 3 model B+ includes a Gigabit wired LAN adapter onboard-though it's still hampered by the USB 2.0 bus speed (so in real world use you get ~224 Mbps instead of ~950 Mbps). Tl dr You can get Gigabit networking working on any current Raspberry Pi (A+, B+, Pi 2 model B, Pi 3 model B), and you can increase the throughput to at least 300+ Mbps (up from the standard 100 Mbps connection via built-in Ethernet).

Usb 2 vs usb 3 vs ethernet