I'm not going to try to convince you to get one or the other. They're both great devices. But I'll just jot down a quick list of the advantages each has.
Galaxy S3
1) Storage. The S3 has a microSD card slot. You can also get a 32GB model of the S3 if you want.
2) Larger removable battery. The battery in the S3 is bigger than the battery in the DNA, plus it can be switched out with a spare battery or extended battery.
3) Software. Sense really hasn't changed much over the past several years, and it really doesn't bring too much to the table besides a different look. While I don't care for the cartoonish look of Touch Whiz, Samsung has really added some stellar features to the software that are very useful. There are a lot of gestures and motion controls, the pop-up video feature, and the potential for multi-window support in a future update just to name a few.
4) Accessories. All versions of the S3 around the world are physically identical (except for the super duper quad-core version with 2GB of RAM that was only released in South Korea). That means you can use any accessory that's compatible with the S3 from anywhere. No other Android phone has the same amount of accessories because no other Android phone is as widely available.
DNA
1) 5" 1080p display
2) Quad-core processor
3) Reception. We don't know this 100% for sure yet, and it can very based upon your location, but historically, HTC devices have had slightly better reception than Samsung devices. I've found the S3's reception to be on par with most HTC devices I've had previously, but if reception is going to go in either phone's favor, it's probably with the DNA.
4) Sound. The Beats Audio is really a gimmick, but what's not a gimmick are the dedicated amplifiers for the headphone jack and the speaker. If you listen to a lot of music, the DNA is likely to sound better. The S3 is no slouch when it comes to audio, but the DNA will have additional hardware that will give it the edge.
Samsung has also been faster with updates for their high end devices over the past couple of years than HTC has, so that's something to potentially keep in mind for the future (although, being on Verizon, both will be slowly than on other carriers). Beyond that, much of the rest is a wash - both have 2GB of RAM, both have excellent cameras, and both will be running Jelly Bean before too long. You really can't go wrong with either device in my opinion. But for me, the 16GB of storage (with only 11GB useable), no microSD slot, and a small, non-removable battery are dealbreakers for the DNA. But that's because of my needs and wants in a device. For people that aren't concerned about those three things, the DNA is a fantastic choice.
Personally, I'll be moving onto the Note 2 as soon as it's released. :biggrin:
