As mentioned before, it depends on what you want.
The OnePlus One has much more power on the inside--it also needs it, due to the nature of Android. But that's not a bad thing, since not only will you have a lot more in the way of high-graphics games, they'll run better than if they were on WP. For daily use, though, the power isn't an advantage--even the most powerful Android handsets aren't particularly fluid, but that's a tiny difference (the actual difference in GUI matters way more).
Likewise, in terms of (free) software--no one beats Android. Of course, you'll also need to worry about malware, adware, and security in general much more.
Aesthetically, you'll need to make the decision your own.
If wireless charging matters to you--zero question. Get a Lumia 830--it has it, the other phone doesn't. End of story. Qi charging doesn't matter to me that much, but a few people are converts who couldn't live without it. Even I think it's pretty slick.
Storage space wise, also no contest--the 830 has a MicroSD card you can switch on the fly. The OnePlus One doesn't. The biggest (64 gb) handset is going to set you back more ($349.99), and is still going to be smaller than a 830 with a MicroSD card (so far, support is up to 128 gb cards).
That goes to cost--if that maters, the 830 is more expensive ($379.99) or cheaper ($279.99) depending on what version you get (though they're the same size). Likewise, some versions of the OnePlus One are more than $400.00. You'll need to do your research as it relates to what region you're in. So this is a bit of a toss-up.
The camera I'm not certain about--the OnePlus One has more video recording options (including 120FPS at 720p and normal speed for 4K), but the Lumia 830's pureview has better stabilization. But the OnePlus One has more megapixels, for what that's worth (13MP vs 10MP), and a better front facing camera. I think the OnePlus One wins in this area, but it's not clear to me either.
Battery wise, the 830 probably wins. Removable battery and its length of use is one of its most common praises. The OnePlus One has a removable back, kind of weirdly, since nothing is accessible through that, including changing the battery.
I think it comes down to what ecosystem you want--that's true for most handsest in the end of the day. If you want Android features, it's no contest, just as if you want WP features. They're both really nice phones, and if I was going to go Android, OnePlus One might be the way to go.
EDIT: Additionally, the 830 has glance--which is a great feature, and I wonder why Android doesn't immediately copy it (then again, not all Lumias have them either--the 930 doesn't). The OnePlus One has some Android specific features too, but nothing like that presently. Again, ecosystem.