Whether he plays the 3 or 4 is dependent on who he can defend (not what he plays offensively). If Murray can play either SF or PF full time, it gives us a lot more flexibility and options from a roster construction perspective.
For instance, if he can defend SFs full time, it could allow us to go sign someone like PJ Washington to be our long term PF. And if Murray’s shot blocking abilities transfer over from college, that gives us two decent rim protectors on the court with Sabonis (Murray and Washington) helping mitigate his weakness while at the same time not sacrificing our defense and shooting at the SF and PF spot.
I’ve said this on the forum before but if you’re trying to maximize a team that has Sabonis on it, you ideally have both a SF and PF who can defend, protect the rim, and space the floor. It’s easier to find that type of player at PF and much more difficult to find it at SF. Murray may possibly be that rare SF but I need to see more.