The way you intend to use the cymbals rather than their pitches is probably the best way to decide where to put them.

Typically, the ride cymbal is placed somewhere where it's going to be comfortable for you to hold your arm for an extended period of time. Since you'll be playing a steady pattern on the ride cymbal through several measures, your arm will start to ache in a hurry if you don't.

Normally, the crash cymbal will go somewhere that's very easily reachable for both hands, but it does not matter if you can hold your arm there for an extended amount of time. The crash cymbal is mostly used for accents, so you will rarely have to hold your arm in position to play it.

So, it definitely is the drummer's choice.  So, if you use both cymbals as rides, you'll find two comfortable positions for a ride cymbal, and then from there, you decide which cymbal you want where. If you want to use one as a crash and one as a ride, you'll put them in places to accomodate that.

Traditionally a right-handed kit will have the crash on the left, near the hi-hat and the ride on the right, usually above the floor tom and to the right of the rack tom/toms.

But as mediablamer said - it's all about what is most accessible and comfortable, and if that turns out to be something unusual or different, don't sweat it - go for it!