This does not seem like a Lightroom question, as the speed of transfer across a network has nothing to do with Lightroom.
You will probably find the same problem happens during a desktop file transfer when Lightroom is not involved.
Wired networking is definitely much faster and more reliable than wireless. An Ethernet cable is a dedicated and fully shielded path that can maintain throughput over a relatively long distance. A wireless connection is subject to all kinds of interference: Competition with other routers and devices on the same band, noise, and performance that drops with distance and obstacles.
If your router and computer use the latest commonly available wifi standard, 802.11ac, the maximum theoretical throughput of that standard is 500 megabits per second (62.5 megabytes per second). But the maximum theoretical throughput of Gigabit Ethernet (available on most computers and routers now) is double that, 1000 megabits per second (125 megabytes/sec).
In practice, both are slower than advertised because you can only get those speeds under absolutely ideal conditions with the best equipment. And the problem is that because wireless has so many more challenges than a nice shielded cable, the difference (the drop in speed) between the theoretical and real world speed of wireless is greater than it is for wired networking. I have seen file transfers peak over 100MB/sec on my wired connection, but I rarely see more than 20MB/sec on my wireless transfers.
If speed is a requirement, it is definitely best to use wired Gigabit Ethernet whenever possible.
Thanks for your response, dj.
I am using LR Classic CC, same as on the old PC. And, if it is not the wireless vs. wired connection to the network causing this, why would my LR file transfers go from fast to slow? The only things that changed was the PC and using wireless. It is strikingly slower with the new PC. And, I agree that "a file is a file", content doesn't matter.
I'm trying learn why the file transfer is so slow on the new PC, where it was not on the old one. I need to fix this ASAP, as the file transfer performance is not acceptable. The NAS is the same unit, same software. Is there a setting somewhere that I didn't toggle correctly?
Thanks, Conrad... This is what I was thinking, too. The network card is a gigabit card, so that is pretty fast. And, the wireless router is essentially new and can service those speeds. So, the CAT 6 cable to the new PC sounds like the answer. I will try that and report back.
OK... the file transfer speed seems to be greatly improved using the CAT 6 cable vs. wireless. At least in the limited testing that I did. And, that all makes sense. I was just resisting moving the cable over the new PC since I still had some files on the old one that I wanted to have access to. But, I can deal with that later.
Thanks for your help!