That is, assuming the user is capable of flashing the HTC One with a third-party firmware to get a vanilla Android experience. Is there a draw to the Nexus in comparison to the likes of the One other than being vanilla out of the box?
The One is the better phone, no doubt, but the Nexus is best for the price.
The One has a much better radio, especially for bluetooth. It's a lot more powerful, a consideration if you're playing games. The screen blows the Nexus' thoroughly mediocre display out of the water, and the stereo speakers are some of the best I've ever heard on a phone. The build quality is closer to Apple than Android. The camera is one of the best on an Android phone ever.
The major downside of the One for me is that it is slower in terms of slickness and smoothness, which I'm blaming on the Sense UI. If you flash it to vanilla, it should be fine. If you are a gamer, it does get very hot. Although build quality is better it doesn't feel any less likely to break if you drop it.
Weirdly, the call quality isn't that good on the One, the Nexus has it beat there.