Earlier in the week I replaced a pair of MX100s running 16.16.3 with a pair of MX250s running the same code.
Looking at the graphs below that show the latency and jitter from this site to another local one that is still running a pair of MX100s, you can clearly see when I swapped them out.
The site's links aren't overloaded, with traffic pretty constantly around 100Mbps across a pair of 230/1000 circuits.