The best replacement for packet size is throughput.

The best alternatives to packet size are rated as following:
★★★★★  throughput
★★★★  frame size
★★★  mtu
  rtt
  through put
  round trip time

Your alternative for packet size is not listed? Suggest!
Speaking about packet size, one probably shouldn't forget about ping.

Other search terms related to packet size and their ratings are:
★★★★★ ping
You have in mind a companion for packet size and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of packet size in all years. Click on graph for more.
packet size
throughput
frame size