Much to my chagrin, I don’t yet have a Ubiquti network, so I can swag but I can’t measure exactly (I have an expansive, 5 access point Apple-based network that refuses to be made redundant, despite all the home networking improvements in the past 10 years). Several other folks on the forum have looked at general Sense traffic with the mothership and within their home network. There’s a good view into how Sense talks to smartplugs here. Suffice it to say that TP-Link is more bandwidth efficient - Sense sends out a broadcast for power info every 2 seconds and all the HS110s/HS300s respond with data. No handshakes.
At one point in time, I thought the congestion from my 32 Kasa outlets (mix of HS110s and HS300s) was causing data dropouts, and moved all my Sense traffic to a different subnet (same physical hardware) to try to improve things, but it turned out the Sense monitor was the weak link. Sense helped me with an adequate workaround, but I probably shouldn’t have changed subnets because I couldn’t move my Hue to the same subnet, so now I can’t use that integration.
Thinking about data flow in my house now, with both kids home from college, I realize that Sense / TP-Link is a very, very small part of the packet traffic.