The Samsung Galaxy Note 3 was released this past October/November, but it is still a good comparison and holds up well to the new HTC One M8. The processors are almost identical and both have a microSD slot for additional internal memory - up to 64GB in the Note 3 and up to 128GB in the HTC One M8.
Other than that these devices are different and quite possibly targeted for different audiences - the HTC One M8 is a classy or sexy looking device and the Galaxy Note 3 is more business like and task oriented. The metal body versus plastic body, the Phablet versus the more traditional smartphone. Look over the specifications listed below and then we will look at each individual device before choosing the winner.
HTC One M8
Let's discuss the aluminum body first because this one of the HTC One M8's main features - HTC increased the metal on the new HTC One M8, eliminating the plastic sides so that the metal actually wraps up around the edges to the display and they also curved the back slightly to make it more comfortable to hold. Some people like the look and feel of metal, although we did hear from one smartphone aficionado who spent a couple of hours with it and just did not like the feel of the metal and others have said it can become very warm or extremely cold, depending on the ambient temperature. Of course wrapping a case around it makes the metal a rather moot point.
One of the biggest changes that HTC made lies within the camera - not that it is the best shooter by any means, but HTC added a second camera called the Duo Camera, which is not really used to take pictures, but to add depth and special effects to your photos. The main 4MP camera is the same UltraPixel camera that was used on the HTC One M7 - a gratifying experience, but certainly not the 'camera-of-the-year.' One of the great things about the M8 are the dual stereo speakers with BoomSound, already much better than any other smartphone out there, and now they are 25-percent louder and with even a richer sound. Many users like Sense 6.0 over the TouchWiz on the Note 3, but it is really a personal preference.
Samsung Galaxy Note 3
The Galaxy Note 3 came out in November and was an instant hit, not that it was that much better than the Note 2 that it replaced, but there were many original Note users that were dying to upgrade and the Note 3 was light years better than the first Note. With the addition of 3GB of RAM and the Snapdragon 800 quad-core clocked at 2.3GHz the Note 3 was the first Samsung device that actually flew through most tasks very smoothly and was a real pleasure to use. The display was beautiful and has the customizable features to choose the display best suited to your tastes. It has the 32GB storage option, but does have a microSD slot for up to an additional 64GB of internal storage. The battery is larger at 3200mAh vs 2600mAh and even though the Note 3 has a larger display, the Note 3 has excellent battery life.
One of the Note 3's more unique features is the built-in S-Pen and more importantly, the Note 3 has software that takes advantage of the S-Pen and really adds productivity to the device - providing you use it. If you need to take a screenshot, take a quick note, do some scrapbooking, a little drawing, manipulate photos and even playing games, the S-Pen can be a big help. Multitasking is better on the Note 3 because of the larger screen and 3GB of RAM. The speaker was moved from the back of the Note 2 to the bottom on the Note 3 - a wise move, but still not up to the HTC One M8's speakers.
...And the Winner is...
I know I will catch flak for this, but I have to pick the Galaxy Note 3 as the overall winner. If all we looked at was the body material, the speakers and price, the HTC One M8 would be the winner without a doubt. But when we look at screen size, RAM, battery, productivity, the added S-Pen, as good or better camera, and some really good software, it has to go to the Galaxy Note 3. Yes, I know that Samsung has a lot of bloatware on their devices, however, some of the options, like Adaptive Display that automatically adjusts the display depending on whether you are watching a movie, looking at pictures, or reading a book, or Air Command really make a difference. Even though the Note 3 is older, it was so packed with specs that it holds up well against this new crop of flagships. While the HTC One M8 does have Android 4.4.2 KitKat, the Galaxy Note 3 will be getting that upgrade very shortly. So while the HTC One M8 is a great looking and sounding device, the Note 3 just has more hardware and software going for it.