I think that any conflict on a national scale inevitably becomes about both, even in cases where it wasn't initially. They are inextricable. The Great War started in an undeniably ideological manner, a political assassination leading to conflict between nations due to alliances and treaties building more and more into a continent wide violent debate of democratic nationalism vs autocratic imperialism.
Though in the end it devolved into squabbling about territory and reparations, which directly led into WW2.

One leads into the other leads into the other. To discuss say WW2 in purely ideological or purely resource based terms is to divorce it from context. That being said, if I had to choose one, it would be ideology. A large scale long term conflict cannot be about nothing, it needs to be happening for a reason that people can grok and rally behind. Simple and powerful. That doesn't have to actually be the actual reason, but it has to be a reason.