I'd pick the 25. (I own both). As it's more versatile.
But then again, it depends what other FLs you're taking on the trip. If you have 24-70 covered, then the 18 gives you a wider option.
I like the 25 for walking around...maybe i will just take both...

So that's kind of a pain... but I don't have to zoom in really at all anymore to see exactly where my focus is, it's pretty sweet kicking back on my sofa while I'm editing too 




