Ethernet Throughput Slower Than Wireless?!

This is an odd one...

I'm experiencing issues with streaming some content (mostly youtube but some other media like netflix and hulu) over a hardwired ethernet connection. Primarily I've noticed the issue with YouTube. See details below:

I'm using an Apple iMac and prefer a hardwired connection (speed, less network interference in my complex...etc.). However, when I use a hardwired connection I have a lot of issues with youtube videos buffering and stalling mid-play.

The funny thing is that when I switch over to a wifi connection (on the same iMac) youtube videos load without a single hiccup or buffer-stall

I'm puzzled as this makes no sense. I run a speed test on my line using both the wifi and ethernet connections and I'm showing roughly the following results both of which shouldn't have any issues playing youtube videos:

over wifi: ~25-30 Mbps down, ~5 Mbps up

ethernet: ~40-45 Mbps down, ~5.5 Mbps up

and yet the ethernet connection is slower for youtube videos than the wifi. I used to be on a 15 Mbps cable internet connection and didn't really have issues with that one and I certainly wouldn't expect to have issues on a hardwired 45 Mbps connection.

could there be some settings within my NVG589 that I should try adjusting? It just doesn't make much sense to me. Any help or suggestions would be greatly appreciated 🙂