They are completely different tools. SopaUI does not test like QTP does where it opens the AUT and starts doing things to it. SOAPUI is more API and load testing.
SOAPUI versus HP UFT versus Powershell for SOAP/REST API testing have all their own pros and cons.
Powershell is powerfull with one line of code you import your wsdl and directly you have the power at your fingertips. So far not anything seen thats more quicker and nice part its on everyone's windows machines including servers.
For HP UFT you have to know the context menu to send away simple xml's in 1-2 seconds otherwise you are compiling which quickly gives you 2-3 minutes delay. The nice flowchart you get as a present from HP UFT for your documentation. Developers probably do not like the VBScripting stuff which is rather outdated language but with power of dotnetfactory object you can also deal from VBScript with .NET namespaces.
SOAPUI is very intuitive when you start it but for the more complex things you have to use Groovy scripting.
@jpulley3 - you are correct: however if it's api testing, UFT API testing is not too bad i think (i am still looking at it as where i work we use both ReadyAPI(SoapUI) and UFT).
However i think this is also purely down to choice of the employer/client as to what tool they are looking at and also how much they are willing to spend
Wouldn't the more natural comparison to SOAPUI be HP Service Test instead of HP QTP?
Service Test no longer exists. It was superceded by UFT back at v11.5 (way back in 2012).
The name change from QTP to UFT is due to the inclusion of the feature set that used to belong to Service Test.