I've killed moose and I've killed elk. Though moose on the average are bigger then elk, elk are tougher.
I've never shot a moose with a 270 but I've killed elk with my Model 70 Featherweight in 270. Its my main hunting rifle and I would hesitate hunting any animal in North America with it.
Since your friend has a 270 and is comfortable with it, its probably the best choice for his moose hunt.
I've found the best bullet for my rifle for elk hunting is the Hornady 150 Interbond. It has good BC but is pricy, almost twice the SST 150.
The thing is the 150 SST and 150 have the same BC, meaning if they are loaded the same they have the same trajectory. The SST is cheaper so I used it for practice and target shooting and save the Interbonds for hunting. One box will last a long time if you save them for hunting and use the SST's for everything else.
The difference between the two is the core is bonded to the jacket in the IB meaning the bullet holds together.
The SST isn't bonded and comes apart, which would be that big of deal on deer and antelope but on elk or moose, I would want a bullet that holds together.
Having said that I still use the IBs on deer and antelope.