Pebble has announced a third device to add to its colour Pebble Time family of smartwatches, with more of a fashion/design focus. The Pebble Time Round is the first watch from the company that comes with a completely circular face but that's not the only difference between it and its slightly older brothers.

It seems like Pebble is slightly branching out with a daintier device but with three new(ish) watches now in its line-up - not including the original Pebble and Pebble Steel - that leaves a quandary as to which to buy if you are in the market for wrist-worn technology.

That's why we look and the design, features and specifications of the Pebble Time Round, Pebble Time and Pebble Time Steel to give you an idea of what they each offer.

READ: This beauty is the Pebble Time Round smartwatch: Here's what it can do

The most obvious different between the three devices is aesthetic. Not only is the Pebble Time Round, well, round, it is far thinner than the other family members. It measures just 7.5mm in thickness, while the Pebble Time is 9.5mm and the Pebble Time Steel is 10.5mm.

All three have stainless steel bezels, although the Pebble Time is plastic behind that. Its bezel is also set in a darker colour (black), while the Pebble Time Round and Steel devices are available with black, silver and rose gold metal finishes.

The Pebble Time is also available in different colours, with the plastic backing available in white and red as well as the aforementioned black.

All of the watches can have different bands attached, with the Pebble Time Round also available in two band sizes: 14mm and 20mm. The Time Steel and Time both use 22mm bands.

READ: Pebble Time review: A smartwatch stepping stone

Bar the shape, all three screens use the same colour e-paper technology, with LED backlighting.

Battery life is quite different across the three devices and clearly related to each watch's depth. The Pebble Time Steel has the best quoted battery life of up to 10 days (which we found to be more like seven in normal use, but that's still impressive). The Pebble Time has the next best battery life claim of up to seven days (five in normal use for us). And the Pebble Time Round claims just two days of battery life in comparison.

We haven't tested the Round yet so are not sure if that stands up in real-life, but one benefit it has is that it can be charged enough for a whole day's use in just 15 minutes.

All three devices are charged through a magnetic attachment on the rear of each watch and a specially adapted USB cable.

READ: Pebble Time Steel first impressions: What we think of the Apple Watch alternative so far

We're not entirely sure at present how many of the Pebble OS apps and watchfaces will work on the Pebble Time Round because of its circular screen, but it runs exactly the same operating system as the others so the potential is huge.

The other two watches can both run exactly the same apps and use the same watchfaces, even the black and white ones from the previous Pebble devices.

In terms of usability, all three watches are the same. They each feature Pebble's proprietary Timeline experience for scrolling through past, present and future notifications, messages, emails and calendar entries. They also have physical buttons rather than touchscreens to do so.

They all have vibrating motors inside to give the wearer silent alerts, and microphones that allow the user to give voice replies to emails (just through Gmail on iOS).

However, only the Pebble Time and Pebble Time Steel are waterproof to 30 metres. The Pebble Time Round is merely splashproof, so not able to be worn in the shower or swimming. It's also worth pointing out that the leather bands provided by Pebble are not waterproof either and should be removed prior to showering if used on a Pebble Time Steel.

The silicone strap that comes with the Pebble Time is fine in water.

All three watches are compatible with Android and iPhone.

As the entry level model, the Pebble Time is the cheapest of the three (you can get a Pebble or Pebble Steel if you are looking for an even more budget model and don't mind the black and white screen). It is £179.99. Both the Pebble Time Round and Pebble Time Steel start at £229.99.

The real decision making for those looking to buy a Pebble smartwatch shouldn't come down to price but what you plan to do with it. There is no denying that the Pebble Time Round is the sleekest in looks, but its two day battery life might not cut it for some.

What might be more important to you is availability, and the UK release of the Pebble Time Round is still to be determined. Pebble says that it will come in 2016, but is not specific about the date. US consumers will be able to get hold of one from November, with pre-orders available now, but if you live in the UK and are looking for a premium smartwatch that isn't an Apple Watch or Android Wear device, you couldn't do much better than the already available Pebble Time Steel.