"Hehe. Fine, we have ourselves a deal." Soran smiled. In such a situation where their live and death was an unknown factor, Soran had to make a proper decision.
Soran might be known as the Blood Beast but he wasn't as wild or reckless as the men of the Savage Tribe. When compared to the Maniac Chief Goro, Soran was a lot more sensible and reasonable. The only reason he had the title 'Blood Beast', was because of his hunger for blood and murder, but that those not mean that he would let his wild nature cloud his judgement so easily. This could easily be seen from the fact that despite continuously challenging him, Soran didn't kill Flood King. If it was Goro in his shoes, a different situation would sure play out.