Test one: Audio quality
When it comes to everyday indoor use, you'd be hard pushed to tell the difference between calls made on any of our five headsets. They all do their jobs perfectly well within the majority of the standard Bluetooth 10-metre range. You might want to think twice about putting a wall between yourself and your iPhone if you don't want your audio cutting out, but for the most part they're fine.
It's when you take them outside or into noisy environments that they show their various strengths. The GameCom P90, though, is meant to be used inside, and while it features a degree of noise reduction, it doesn't feature the advanced wind-silencing features of the other headsets.
Putting the P90 aside, the best of the bunch is undoubtedly the EtyBlu2. It's built with call quality in mind, from the flexible boom mic to the noise-isolating earpiece that, with the right eartip, blocks out an impressive amount of noise. If call clarity is your priority then read no further; nothing touches the EtyBlu2.
That said, the Jawbone Era isn't far off, with its military-grade noise reduction systems. NoiseAssassin 3.0 - its catchily named noise-cancellation tech - was developed for use by tank commanders and helicopter pilots, and it does a great job, so much so that the fiddly way of adjusting the earpiece volume doesn't bother us.
Both the Nokia BH-609 and Jabra Wave perform just as well in adverse conditions, each with their own special ways of dealing with unwanted noise. The Nokia packs two microphones for noise reduction, while the Wave has three-layer noise protection as well as digital signal processing.
The general upshot is that between these two and the Jawbone there's really not a lot to differentiate them, audio-wise, and unless you work with a pneumatic drill you're unlikely to run into situations where you can't hear or be heard.
Test two: Comfort
Comfort's such a subjective thing, isn't it? Thankfully, none of the headsets here actually hurts to wear, although the GameCom P90 is just a little on the snug side; we can envision chaffing after a long session.
Interestingly, the EtyBlu2 feels the least stable thanks to its long microphone boom; we wouldn't want to wear it without an earloop, and its deep in-ear fit is a little unsettling.
The Nokia similarly needs an earloop to avoid droop, while the Jabra Wave's over-the-ear design and rounded frame make it sit nicely around the ear.
However, the chunky but featherweight Jawbone Era wins out definitively here; we've found it to be the only one that can sit happily in the ear without earloop support and remain in place.
Test three: Design and features
The most striking of our five headsets is the EtyBlu2, with a functional, almost industrial design clearly aimed at sustained use.
Its most notable features are splendid examples of form following function; the long and flexible boom microphone serves to catch your voice more effectively, while the earphone is designed to be wedged right into your ear and block out background noise, and sounds accordingly great. Its one multi-function button (there are volume controls, too) feels a little stiff, but once you've taken a couple of seconds to learn how long to press it to do what, it works just fine.
The Jabra Wave has a similarly stand-out design; it's built to curve round your ear and, once there, it stays in quite happily. You do all your call-taking and hanging up functions with a squeeze of the button built into the microphone, while power and volume controls sit on the main body of the headset, behind the ear and easy to reach.
The other three headsets are similar compact earpiece designs. The GameCom P90 is by far the cheapest of the three and it shows. It's very plastic and feels flimsy, but remember that it's meant for teenagers calling each other unrepeatable names while playing Call of Duty online, not for CEOs putting in a call to head office on the way home because they forgot to fire Perkins. And despite feeling like something you might win in a cracker, the P90 works well, with a multi-function button and volume controls that click nicely.
The Nokia BH-609's a longer, more slimline design that doesn't feel especially solid; we have it marked down as the most likely to come to a crunchy end if you accidentally step on it. As well as the standard multi-function button, it also comes with an extra 'My own key' that you can load with up to three special functions; or at least you could if you were using it with a Nokia phone, so for our purposes it's dead weight.
Which leaves us with the Jawbone Era, the only one that you can look at and believe that someone made an effort to create something nice to look at. Its textured faceplate, its accelerometer-powered functionality (tap it to answer and hang up, shake it to pair it with your phone), its voice messages and its apps; none of it is strictly necessary but all of it works, resulting in a headset that even we're happy to show to people without any sense of shame. It's pretty and light and balanced and a bit mental as well. Hooray!
And the best iPhone Bluetooth headset is… Jawbone Era - £74
Look, we have this sneaking suspicion that technically the best bit of Bluetoothery in our round-up is the EtyBlu2. It's just so professional, with its flexible boom microphone and deep fitting. It features an intimidating horde of technologies aimed at delivering sound and eliminating noise and, frankly, it's boring.
Do a Google image search for 'professional' and you'll see a load of stock photography of the sort of person the EtyBlu2 is meant for. And that's all fine for them. If you are a serious business person along those lines, we thoroughly recommend it.
But if we're going to nail our colours to the Bluetooth headset mast, we simply have to go for the Jawbone Era, because it's a perfectly decent headset and because it's utterly preposterous, from the very moment that it starts up and tells you that it's making a startup noise. Even if you only pair it the once, won't you feel better by shaking the Era rather than holding down a button for five seconds? Of course you will.
Same goes for answering and hanging up just by tapping on it. It's like being in Star Trek. It's also the only one that offers A2DP, meaning it'll handle audio other than phone calls, and while you'd be a fool to listen to music with it, it's brilliant as a little in-ear speaker for your iPhone, just right for when all you want is a little auditory feedback for games and don't really want to wear earphones.
Oh, and while all our headsets will gladly pair with an iPod touch or iPad, the Era's the only one that'll do anything at all once paired.
Crucially, it's really tiny, light and comfortable; we're not sure you'd ever forget that you're actually wearing it, but you're a lot more likely than with the other headsets.
The Jabra Wave comes close in that regard with its clever behind-the-ear design, and we have quite a soft spot for it. It's cheaper than both the Era and EtyBlu2, features decent audio technology and, appearance-wise, it's pleasantly understated and relaxed. If you go down the headset shop and they've run out of Jawbones, you won't feel bad about making do with the Jabra Wave.
The mostly great Nokia BH-609, with its super-special extra button that doesn't work on the iPhone, is simply not for us, we suspect.
And as for the GameCom P90… it's not brilliant, but then it's not designed to be an all-round Bluetooth headset; it's designed primarily to be used with a games console and it's £16. Honestly, if you're not sure that you actually need a Bluetooth headset, then £16 for the P90's a steal.