The phone market is smaller than people think. If you eliminate iPhone or a Samsung, the phones I list above are, IMO, the only clearly comparable alternatives. If you are buying off-contract and trying to save money, the OnePlus is the only real option (the Moto G is a distant second place in this category).

After that, if you want a big-ole phablet, the Nexus 6 is going to be excellent (but huge).

Between the HTC One, Moto X, and LG G3, I'd give the node to the Moto X first, but your choice is going to come down to a lot of preference. I lean toward the Moto X because it offers a near-stock-android experience, will get Android updates quickly, and has reviewed very, very well.

I'll add a plug for a Nexus 5, as well. This is my current phone. If the price stays at $349 (off contract), then it is a little overpriced. If that price comes down, it is a great purchase. The only knock on the N5 is battery life on other phones is better. If you are a "heavy" user, it struggles to get through a day.