The best replacement for soapui is jmeter.

The best alternatives to soapui are rated as following:
★★★★★  jmeter
★★  selenium
★★  loadui
★★  soatest
★★  soapsonar
★★  hp service test
★★  testcomplete
★  loadrunner
★  soapui pro
★  lisa
★  postman
  fitnesse
  xmlspy
  green hat
  soap sonar

Your alternative for soapui is not listed? Suggest!
Speaking about soapui, one probably shouldn't forget about fiddler.

Other search terms related to soapui and their ratings are:
★★★★★ fiddler
★★★★ rest service
★★★★ client certificate
★★★ groovy
★★ wshttpbinding
★ hermesjms
You have in mind a companion for soapui and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of soapui in all years. Click on graph for more.
soapui
jmeter
selenium