I'd keep in mind the HTC One is brand new, and you probably won't find many informed opinions on it yet.
Ars Technica did a pretty in depth hands-on with it:http://arstechnica.com/gadgets/2013/05/htc-one-review-its-now-or-never-again/
I'm inclined to say that the Galaxy S 4 is still the Android phone to beat, if only because HTC's Sense 5 is too grating for my normal TouchWiz ways. Although Samsung's TouchWiz UI has its own follies, it feels like it's still an Android experience, though it's not Google's. The One's UI doesn't feel so much like Android, although I instinctively know how to swipe around to get to what I need within Sense 5.
The HTC One also attracted more attention than the Galaxy S 4 did when I used it in the real world. It was the aluminum chassis that caught onlookers' eyes at first, and the general consensus was that the HTC One felt better in the hand. This is really a matter of personal preference, and while I don't like that HTC has made some changes to Android that I'm not too keen on—the lack of a Menu button and the BlinkFeed takeover, for instance—it's no different from what any other OEM is doing with its Android handsets that aren't a part of the Nexus program.
There's also a bit to be said about the construction of the HTC One. As Brian Klug at Anandtech pointed out in his review of the device, HTC has created a design story for the One that gives it some Apple appeal. Rather than try its hand at branding through a flagship name—like Samsung has done with its Galaxy line of phones—HTC will instead attempt to gun for the design savvy with its “zero-gap” construction. It must be working, because even at-a-glancers seem to like what they see in the One's aluminum construction and design.
Now, not that I know crap about this (I'm a happy iPhone user since last year), but I think it's more do you want a fancy pants aluminum case with front firing amplified speakers, or not.