There are three buttons on the device. The first is an on/off button, the second is primarily a direct-to Handsfree Assistant button (more about this later), and the third is a multifunction button (answer call / end call / voice dial & redial) that doubles as a large dial for volume up and down. Compared to the Crystal, these buttons are a pleasure to use. It's particularly nice to turn up or down the volume on a call using the dial.
Similarly to the Crystal, the HD has a magnet on the rear so you can attach it to the included clip, making it easy to attach to a car visor or other convenient spot. The clip also doubles as a mount for when you place it on a desk or counter. As mentioned in the Crystal review, the design is simple, but it's effective.
The HD shares many of the same specs as its smaller sibling. Battery life (20 hours talk, 1000 hours stand by) and Bluetooth range (around 10 meters) are the same. Where the HD takes ground on the Crystal is with its louder speakers (with a 5.4 Watt class D amplifier), noise cancelation and dual microphones for better audio quality. There's also the HandsFree Assistant, but I'll come to that in a few paragraphs.
Considering I didn't encounter a scenario where I needed the Crystal's speaker to be louder than what it has to offer, I'd say the HD's boost in volume is not necessary, but welcome. Particularly for those rare, but exceptionally loud environment moments. At top volume, the HD is incredibly loud. In fact, it's uncomfortably loud. But unlike the Crystal, there's very little distortion at full volume. The HD's class D amplifier and new speakers do pay off in this area. Full volume on the Crystal is a distorted mess.
Similarly, in my tests with the Crystal, I didn't struggle with others hearing my voice. However, with the HD in those particularly loud environment moments, the noise cancellation did seem to help with clarity for those on the other end.
Two of the biggest selling points of the HD are its voice feedback / interaction and HandsFree Assistant support from Dial2Do. Unfortunately, both are its biggest draw back. These two features represent a very bad attempt at Siri-like interaction from SuperTooth on the HD.
First off, the voice commands (like calling a contact with your voice) require you to sync your address book to the HD. Unfortunately, this process is anything but simple. The HD spent a good few minutes copying my address book over, but from what I can determine, it can't use the formatting of an iOS address book, which means it doesn't recognise my contacts. I tried any number of ways to get this to work, but I hit a dead end. Visiting SuperTooth's website yielded poorly laid out support which was difficult to follow and didn't fix the problem. SuperTooth also says the HD's firmware can easily be updated, but there is no where on the site where you're told how to do this.
Secondly, the HD's ability to send text messages, tweets and Facebook updates relies on Dial2Do through the HandsFree Assistant button. I'll only say this about Dial2Do: do not bother going there. If you have an iPhone, or any other smartphone, it makes no sense. I'd even hesitate to recommend it to those with dumb phones. In this day and age, there's just no point.
Worst of all, all these features and more are built into Siri and iOS. And you can access Siri through the HD, though it's a two-step process to get there. Ironically, accessing Siri on the Crystal is a one step process. It begs the question: why try to replicate features in a speakerphone that the phone itself can perform significantly better?
It's hard to recommend the SuperTooth HD when two of its main selling points are basically obsolete to iPhone users. And with that in mind -- even though the HD has slightly better looks, a louder speaker and noise reduction -- you'd be crazy to spend $129 on the HD when you can get the SuperTooth Crystal for half the price and simply augment the powerful features that iOS already has to offer.
Check out the SuperTooth HD and Crystal at the SuperTooth Store website.