Load Test : SoapUI Pro vs. LoadRunner

We currently use mercury LoadRunner for our performance testing (mainly through GUI) . We want to start directly load testing SOAP based service.

How does SoapUI compare in general with LoadRunner way of doing performance testing? (tool approach / design / architecture)

Does threads in SoapUI Pro corresponds to virtual users in LoadRunner

Does SoapUI Pro have IP spoofing feature? How does it simulate unique user from unique IP ?

How many virtual users (threads) does SoapUI Pro support?