For elk I perfer the 338 win mag, but both are fine elk guns. The 300 RUM you have to use premium bullets suchas the Nosler Partition, because most 30 caliber bullets was not designed to be shooting at the velocities of the RUM. If you get a close shot and are not using a very good designed bullet, you will have bullet failure. The 338 has been arround along time and the bullets that are available for it were designed arround that cartridge and there really is no need for the extra expense of purchasing a premium bullet. I love my 338 win mag and if I was to be buying a elk rifle, I would strongly concider it the best choice of the two. JMO.