Well, there is one more things to consider at this point: readily available ammo
God forbid, but if the airlines at the last minute decides it does not want you flying with ammo (it happens, trust me, on more than one occassion), then you're up a certain creek, with no paddle...
With the 300WM you can go to the local store and buy whatever they have, in one case, sitting next to the frozen foods... no kidding, in Hungary). With anything more exotic (even the .30-338) you're out of luck and probably a whole lot of $$$, sitting in a foreign land and no gun to shoot with.
But this is probably a minor issue for most. Have not looked at the 300rum or the 338Rum, but will definitely look into it.
Thanks all!